conversion of co2 to carbonates catalyzed by ionic liquids ......conversion of co2 to carbonates...

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Conversion of CO2 to Carbonates Catalyzed by Ionic Liquids under Mild Conditions

Meng, Xianglei

Publication date:2019

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Link back to DTU Orbit

Citation (APA):Meng, X. (2019). Conversion of CO

2 to Carbonates Catalyzed by Ionic Liquids under Mild Conditions. Technical

University of Denmark.

https://orbit.dtu.dk/en/publications/e5f5d6b9-3d57-453b-8196-cc06efa7ea86

DTU Chemical EngineeringDepartment of Chemical and Biochemical Engineering

Conversion of CO2 to Carbonates Catalyzed by Ionic Liquids under Mild Conditions Xianglei Meng

Conversion of CO2 to Carbonates Catalyzed

by Ionic Liquids under Mild Conditions

Center for Energy Resources Engineering

Department of Chemical and Biochemical Engineering

Technical University of Denmark

DK-2800 Kgs. Lyngby, Denmark

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Conversion of CO2 to Carbonates Catalyzed

by Ionic Liquids under Mild Conditions

Ph.d. Thesis

By

Xianglei Meng

Supervisor: Nicolas von Solms (DTU)

Co-supervisors: Xiaodong Liang (DTU)

Suojiang Zhang (IPE)

Xiangping Zhang (IPE)

May, 2019

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Preface

This project is supported by Department of Chemical and Biochemical Engineering

(KT) Technical University of Denmark (DTU) and Institute of Process Engineering (IPE),

Chinese Academy of Sciences.

I would like to first thank my supervisors Nicolas von Solms and Suojiang Zhang to

give me this good opportunity to learn from both DTU and IPE. My main supervisor

Nicolas is one of the nicest and easy-going people I have ever seen. Thanks for your kind

help and understanding, and I would like to express my sincere respect to you.

My co-supervisors from IPE, Suojiang Zhang and Xiangping Zhang, I am grateful

for your help and for your care and attention in both study and life. Your attitudes to

scientific research have always encouraging me to learn from you and improving myself.

My co-supervisor from DTU, Xiaodong Liang, you really gave me so much help, and

solved me a lot of problems. I would like to thank your kind help.

My colleagues at CERE, DTU. I would like to thank you all. It’s really the happiest

time of my life to work with you at CERE. Specially Yingjun Cai and Meng Shi, thank you

for the great help in both life and study, we look like a family.

My colleagues at IPE. I would like to thank for all your kind help on my research study.

To my co-operators Ting Song and Zhibo Zhang, thank you for supporting and

encourage.

My wife, thank you for supporting and understanding me.

Finally, I would like to thank for the financial support of National Key R&D Program

of China (2018YFB0605802).

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Abstract

The utilization of CO2 as a raw material is always a hot topic in both academic and

international industry. The synthesis of five-membered cyclic carbonates by cycloaddition

of CO2 with epoxides is one of the typical feasible routes. Ionic liquids (ILs) have been

widely reported in the cycloaddition reaction of CO2, because of the unique features such

as high thermal and chemical stability, easy recyclability, and tunable properties.

Although most of the ILs catalyst systems show a good yield to produce carbonates, high

energy inputs such as high temperatures and/or high CO2 pressures are always needed.

For energy saving reasons, we designed a series of functional ILs and used them to

catalyze the cycloaddition reaction of CO2 with epoxides under mild conditions. The major

work and results for this dissertation are summarized as follows:

1. Carboxylic acid-based ionic liquids (CAILs) were designed and synthesized. They

displayed temperature-dependent dissolution−precipitation transitions in propylene

carbonate (PC) by controlling the chain length of the carboxyl group. It was found that it

could be attributed to the temperature-controlled hydrogen-bond formation/broken

between the CAILs components and PC by NMR investigations and DFT calculations.

Such a unique phase behaviour was successfully utilized for the cycloaddition reaction of

CO2 with epoxides. Due to the activation of epoxide assisted by the hydrogen bond, the

optimal ILs could show a 92% yield of PC within 20 min and quickly precipitate out from

a homogeneous system at room temperature for easy recycling. The reversible phase

transition phenomenon supplied an efficient way to combine activity and recovery of

homogeneous catalysts, which is a benefit for energy-saving and industrial applications.

2. An efficient 1,8-diazabicyclo- [5.4.0] undec-7-ene (DBU) based bifunctional protic

ionic liquids (DBPILs) was easily prepared by acid-base reaction at room temperature.

DBPILs that composed by alkoxy anion, protic acid and nucleophilic groups exhibited

high activity for the coupling reaction of CO2 and epoxide under mild conditions. As a

metal free catalyst, the best DBPILs showed a 92 % yield of products within 6 hours at

30 oC and 1bar CO2 without any solvents and co-catalysts. And it could afford carbonates

in good yields with broad epoxide substrate scope and CO2 from simulated flue gas (15%

CO2/85% N2). IR spectrum and DFT studies were carried out to invest the mechanism of

the cycloaddition reaction. The results showed that the DBPILs could activate both CO2

and epoxide by the alkoxy anion and powerful hydrogen-bonding, which was well

consistence with experiments.

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3. DBU based ionic liquids containing aluminium (DILA) catalyst was synthesized

based on dissociating feature of proton from DBPILs. DILA was used as a single-

component and solvent-free catalyst for the conversion of CO2 to cyclic carbonates with

epoxide at mild conditions. DILA showed a catalytic activity of 94% within 6 h in catalyzing

the reactions of CO2 with epoxides at 30 oC and 1 bar CO2, because of the efficiently

activating epoxides by the aluminum ions. The effect parameters such as temperature,

reaction times and catalyst dose were investigated. Furthermore, DILA was found

suitable for a broad epoxide substrate scope and could be easily recycled at least four

times without obviously loss of activity.

4. A series of cross-linked poly (vinylimidazole/butyl acrylate) ionic liquids

membranes (PVBILs) were prepared and used as highly efficient heterogeneous

catalysts for fixation of CO2 with epoxide at mild conditions. PVBILs could show

comparable activities in the coupling of epoxide and CO2 with the traditional homogenous

catalysts, because of the activity of CO2 and “homogenous-surroundings” caused by

swellable properties. Swelling behaviour was studied and found to be consistent with the

experimental results of the catalytic activity. The dependence of conversion yield on

catalyst dose, reaction temperature and time were investigated. The best PVBILs could

show a 90% yield of carbonate within 24 hours at 50 oC and 1 bar of CO2.

5. A series of metalloporphyrin ionic liquids (MPILs) that combine the advantages of

ionic liquid and porphyrin were designed and synthesized by one step method. The

structure and surface appearance of these BPILs were investigated. These BPILs

catalysts have multiple active sites and a good capacity of visible light absorption due to

the advantages of functional ionic liquids and metal porphyrin part, thus can reduce the

energy inputs greatly by using the visible light. They were successfully used as a

photocatalyst in cycloaddition reaction of CO2 with epoxide to produce carbonate at room

temperature and 1 bar pressure under irradiation of a visible light.

Key words: Ionic liquids, Epoxide, Conversion of CO2, Mild conditions, Cyclic carbonate.

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Resumé

Udnyttelsen af CO2 som råmateriale er altid et varmt spørgsmål i både den

akademiske verden og den internationale industri. Syntesen af cykliske carbonater ved

cykloaddition af CO2 med epoxider er en af de typiske gennemførlige reaktionsruter.

Ioniske væsker (IL'er) er blevet rapporteret bredt i cykloadditionsreaktionen af CO2 på

grund af de unikke egenskaber som høj termisk og kemisk stabilitet, let

genanvendelighed og justerbare egenskaber. Selvom de fleste IL-katalysatorsystemer

viser et godt udbytte for at fremstille carbonater, er der altid brug for høje energiindgange

såsom høje temperaturer og / eller høje CO2-tryk. Af energibesparende årsager designer

vi en række funktionelle IL'er og anvendte dem til at katalysere cykloadditionsreaktionen

af CO2 med epoxider under milde forhold. Arbejdet og resultaterne for denne afhandling

er opsummeret som følger:

1. Carboxylsyrebaserede ioniske væsker (CAIL'er) blev designet og syntetiseret. De

viste temperaturafhængige opløsnings-udfæ ldningsovergange i propylencarbonat (PC)

ved at kontrollere kædelængden af carboxylgruppen. Det blev fundet, at det kunne

henføres til den temperaturstyrede hydrogenbindingdannelse / bruddet mellem CAILs-

komponenterne og PC'en ved NMR-undersøgelser og DFT-beregninger. En sådan

enestående faseadfæ rd blev med succes udnyttet til cykloadditionsreaktionen af CO2

med epoxider. På grund af aktiveringen af epoxid assisteret af hydrogenbindingen kunne

de optimale IL'er vise et 92% udbytte af PC inden for 20 minutter og hurtigt udfæ lde fra

et homogent system ved stuetemperatur for nem genbrug. Fænomenet om reversibel

faseovergang leverer en effektiv måde at kombinere aktivitet og genopretning af

homogene katalysatorer, hvilket er en fordel for energibesparende og industrielle

anvendelser.

2. En effektiv 1,8-diazabicyclo- [5.4.0] undec-7-en (DBU) -baseret bifunktionel

protisk ionisk væske (DBPIL) blev let fremstillet ved syrebase-reaktion ved

stuetemperatur. DBPIL'er, der består af alkoxyanion, protisk syre og nukleofile grupper,

udviser høj aktivitet for koblingsreaktionen af CO2 og epoxid under milde betingelser. Som

en metalfri katalysator viste de bedste DBPIL'er et 92 % udbytte af produkter inden for 6

timer ved 30 °C og 1bar CO2 uden nogen opløsningsmidler og co-katalysatorer.

Carbonatudbyttet var godt i et bredt concentrationsområde for epoxid substrat og CO2 fra

simuleret røggas (15% CO2 / 85% N2). IR spektrum og DFT undersøgelser blev udført for

at undersøge mekanismen i cycloaddition reaktionen. Resultaterne viste, at DBPIL'erne

VII | P a g e

kunne aktivere både CO2 og epoxid ved alkoxyanionen og kraftig hydrogenbinding, i

overensstemmelse med forsøgene.

3. DBU-baserede ioniske væsker indeholdende aluminium (DILA) katalysator blev

syntetiseret baseret på DBPIL'ernes evne til at fraspalte en proton. DILA blev anvendt

som en enkeltkomponent og opløsningsmiddelfri katalysator til omdannelse af CO2 til

cycliske carbonater med epoxid ved milde betingelser. DILA viste en katalytisk aktivitet

på 96% inden for 6 timer ved katalysering af reaktionerne af CO2 med epoxider ved 30 °C

og 1 bar CO2 på grund af aluminiumionernes effektive aktivering af epoxiderne.

Effektparametre såsom temperatur, reaktionstider og katalysatordosis blev undersøgt.

Desuden blev DILA fundet egnet i et bredt concentrationsområde af epoxidsubstrat og

kunne let genvindes mindst fire gange uden åbenbart tab af aktivitet.

4. En serie af poly (vinylimidazol / butylacrylat) ioniske væskemembraner (PVBIL'er)

med tvæ rbindinger blev fremstillet og anvendt som højeffektive heterogene katalysatorer

til fixering af CO2 med epoxid ved milde betingelser. PVBIL'er kunne vise

sammenlignelige aktiviteter i koblingen af epoxid og CO2 med de traditionelle homogene

katalysatorer på grund af aktiviteten af CO2 og "homogene omgivelser" forårsaget af

svulmeegenskaber. Opsvulmingen blev undersøgt og fundet at væ re i overensstemmelse

med de eksperimentelle resultater af den katalytiske aktivitet. Afhængigheden af

konverteringsudbytte af katalysatordosis, reaktionstemperatur og tid blev undersøgt. De

bedste PVBIL'er kunne give et 90% udbytte af karbonat inden for 24 timer ved 50 °C og

1 bar CO2.

5. En række metalloporphyrin ioniske væsker (MPIL'er), der kombinerer fordelene ved

ionisk væske og porfyrin, blev designet og syntetiseret ved en-trins metode. Disse BPILs

struktur og overfladeudseende blev undersøgt. Disse BPIL-katalysatorer har flere aktive

steder og har en god kapacitet for absorption af synligt lys. På grund af fordelene ved

funktionelle ioniske væsker med metalloporfyrin, kan energibehovet reduceres kraftigt

ved at anvende synligt lys. De blev med succes anvendt som en fotokatalysator i

cykloadditionsreaktion af CO2 med epoxid til fremstilling af carbonat ved stuetemperatur

og 1 bar tryk under bestråling af synligt lys.

Nøgleord: Joniske væsker, Epoxid, Omdannelse af CO2, Svage betingelser, Cyclisk

carbonat.

VIII | P a g e

Contents

Preface ........................................................................................................... III

Abstract .......................................................................................................... IV

Resumé .......................................................................................................... VI

Contents ...................................................................................................... VIII

Chapter 1. Introduction ................................................................................ 11

1.1 Ionic liquids ............................................................................................................ 11

1.1.1 Definition of ionic liquids ............................................................................ 11

1.1.2 Categories of ionic liquid ........................................................................... 12

1.2 Utilization of CO2 ................................................................................................... 13

1.3 Conversion of CO2 to cyclic carbonates ............................................................ 14

1.3.1 Routes to synthesis cyclic carbonates .................................................... 14

1.3.2 Catalysts for synthesis cyclic carbonates ............................................... 15

1.3.3 Cycloaddition of CO2 and epoxide under mild conditions .................... 27

1.4 Research contents ................................................................................................ 31

Chapter 2: Temperature-Controlled Reaction-Separation for Conversion

of CO2 to Carbonates with Functional Ionic Liquids Catalyst ........................ 33

2.1 Introduction ............................................................................................................ 33

2.2 General information .............................................................................................. 35

2.3 Experimental section ............................................................................................ 36

2.3.1 Main equipment .......................................................................................... 36

2.3.2 Synthesis of catalysts ................................................................................ 36

2.3.3 Characterization of the catalysts .............................................................. 36

2.3.4 1H NMR and 13C NMR of Products .......................................................... 38

2.3.5 Procedure of the cycloaddition reaction of CO2 with propylene oxide 39

2.3.6 Reaction equipment ................................................................................... 40

2.4 Results and discussion ........................................................................................ 40

2.5 Conclusions ........................................................................................................... 52

Chapter 3: Efficient Transformation of CO2 to Cyclic Carbonates by

Bifunctional Protic Ionic Liquids under Mild Conditions ................................. 53

3.1 Introduction ............................................................................................................ 53

3.2 General information .............................................................................................. 55


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3.3.2 Characterization of the catalysts .............................................................. 58

3.3.3 Procedure of the cycloaddition reaction of CO2 with epoxide .............. 58

3.3.4 Recycle experiment .................................................................................... 58

3.3.5 Characterization of the catalysts and cyclic carbonates ...................... 59


3.4.1 Activities of various catalysts .................................................................... 63

3.4.2 Effect of reaction conditions ...................................................................... 64

3.4.3 Catalytic activity of epoxides with simulated flue gas and SO2 ........... 66

3.4.4 Catalytic activity to various epoxides ....................................................... 67

3.4.5 Recycling of the catalyst ............................................................................ 68

3.4.6 Studies of reaction mechanism ................................................................ 71

3.4.7 Probable mechanism for fixation of CO2 with epoxide ......................... 73

3.5 Conclusions ........................................................................................................... 74

Chapter 4: Aluminium-containing Ionic Liquid for Cycloaddition of CO2

with Epoxides under Mild Conditions ................................................................ 76

4.1 Introduction ............................................................................................................ 76


4.2.1 General information .................................................................................... 78


4.2.3 Characterization .......................................................................................... 79


4.2.5 Recycle experiment .................................................................................... 83




4.3.3 Catalytic activity to various epoxides ....................................................... 87

4.3.4 Recycling of the catalyst ............................................................................ 88

4.3.5 Probable mechanism ................................................................................. 88

4.4 Conclusions: .......................................................................................................... 89

Chapter 5: Poly Ionic Liquids Based Membranes as Highly Efficient

Heterogeneous Catalyst for Conversion of CO2 to Cyclic Carbonate under

Mild Conditions ...................................................................................................... 90

5.1 Introduction ............................................................................................................ 90

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5.2.1 General information .................................................................................... 91

5.2.2 Synthesis of catalyst used in this study. .................................................. 92

5.2.3 Characterization .......................................................................................... 94


5.2.5 Swelling ratio measurement...................................................................... 96




5.3.3 Catalytic activity to various epoxides ..................................................... 100

5.3.4 Recycling of the catalyst .......................................................................... 101

5.3.5 Probable mechanism ............................................................................... 102

5.4 Conclusions ......................................................................................................... 102

Chapter 6: Biological Porphyrin Ionic Liquids as Photocatalysts for

Conversion of CO2 to Carbonates ................................................................... 104

6.1 Introduction .......................................................................................................... 104

6.2 General information ............................................................................................ 105

6.3 Experimental section .......................................................................................... 106

6.3.1 Synthesis of catalysts .............................................................................. 106

6.3.2 Characterization of the catalysts ............................................................ 107

6.3.3 Procedure of the cycloaddition reaction of CO2 with epoxide ............ 107

6.3.4 Characterization of the catalysts and cyclic carbonates .................... 108

6.4 Results and discussion ...................................................................................... 110

Conclusions and future work .................................................................... 112

References................................................................................................... 114

APPENDICES ............................................................................................. 139

The Cartesian coordinates for Chapter 2 ............................................... 139

The Cartesian coordinates for Chapter 3 ............................................... 157

Abbreviation list ........................................................................................... 178

Peer reviewed journal articles .................................................................. 181

Conference presentations ......................................................................... 181

11 | P a g e

Chapter 1. Introduction

1.1 Ionic liquids

1.1.1 Definition of ionic liquids

Room temperature ionic liquids (RTILs) is a new kind of medium and green

solvent that have been widely reported in various fields[1–3]. It is defined as a liquid

organic salt, which entirely composed of organic cations and organic/inorganic

anions at/ near room temperature. As compared with traditional inorganic salts and

organic solvent, ionic liquids (ILs) have some unique advantages for the iconicity

and liquid properties. For example: 1) Ionic liquids have a wide range of liquid

temperature. 2) Ionic liquids have almost no vapor pressure, which can be used in

high vacuum systems, whilst reducing the environmental pollution caused by

volatilization. 3) Ionic liquids have a good chemical and thermal stability and

excellent oxidation resistance. 4) Ionic liquids have good solubility for a large

number of inorganic/organic substances. 5) Ionic liquids have dual effects of solvent

and catalyst, and can be used as both green solvent and catalyst in the reaction. 6)

Ionic liquids have a high electrochemical stability, high conductivity and a wider

electrochemical window. 7) The properties of the ionic liquid can be easily designed

by the choice of anion and cation thus has a possibility to establish new features

and functions.

In 1914 Walden et al. first reported ethylamine nitrate, a liquid salt at room

temperature (melting point 12 °C)[4]. However, the application of the ethylamine

nitrate is limited, because of the explosiveness of ethylamine nitrate. After many

years studies of ionic liquids by a large number of researchers, ionic liquids have

been widely reported in organic synthesis, catalytic reactions, electrochemistry,

material science, extraction and separation, life sciences, environmental science,

engineering and other fields.[5–9] With the development of ionic liquids, the

definition of ionic liquids is not only limited to liquid at room temperature. The broad

definition of ionic liquids is an organic salt composed of organic cations and

organic/inorganic anions with a melt point below 100 oC.

12 | P a g e

1.1.2 Categories of ionic liquid

1.1.2.1 Traditional ionic liquids

There are mainly four kinds of cations in traditional ionic liquids: alkyl-substituted

imidazolium ions [Cnmim]+; alkyl-substituted pyridinium ions [Cnpy]+; alkyl-

substituted quaternary ammonium ions [NRxH4-x]+ and alkyl-substituted quaternary

phosphonium ions [PRxH4-x]+. The structures of these four typical cationic are shown

in Figure 1.1.

Figure 1.1 Typical cations of common ionic liquids

Ionic liquids can be divided into two categories based on the anion. The first-

generation ionic liquids are composed by the halo salt and AlCl3 (or AlBr3, InCl3,

FeCl3), such as [bmim]Cl-AlCl3 etc. But they are extremely sensitivity to water, and

the usage of these ionic liquids should be under a vacuum or inert atmosphere

condition. The drawbacks limited the study and application of the first-generation

ionic liquids. The second generation of ionic liquids developed on the basis of

reported [emim][BF4] ionic liquid with a melting point of 12 °C in 1992.[10] Unlike the

first generation of ionic liquids, the second generation ionic liquids are stable in

water and air. The anions of the second generation ionic liquids mainly include:

[BF4]-, [PF6]-, [CF3SO3]-, [(CF3S2)2N]-, [C3F7COO]-, [C4F9SO3]-, [CF3COO]-,

[(CF3S2)3C]-, [SbF6]-, [AsF6]-, [N2]-, [NO3]-, [HSO4]- etc.

1.1.2.2 Functional ionic liquids

With the development of the ionic liquids, the traditional ionic liquids cannot meet

the needs of research and applications, thus many ionic liquids with special

functional groups on the anion and cation of traditional ionic liquids are well

developed and reported, such as amino groups,[11] carboxylic acid groups,[12]

ester groups,[13] cyano groups,[14] hydroxyl groups,[15] ether groups[16] and thiol

13 | P a g e

group.[17] Due to the special functional groups, these functionalized ionic liquid

have been widely used in catalysis, organic synthesis, extraction separation,

preparation of materials and the like. In addition, the physical properties (such as

fluidity, conductivity, liquid range, etc.) and chemical properties (such as polarity,

acidity, coordination ability, solubility, etc.) of functionalized ionic liquids are quite

different from those of conventional ionic liquids. In recent years, several novel

cations have been reported, such as cyclic guanidine ionic liquids, pyrrole ionic

liquids, 1,2,4-Triazole ionic liquids, 1,8-Diazabicyclo [5.4.0] undec-7-ene (DBU) ionic

liquids, protonic ionic liquid, crowned ionic liquids, which exhibited unique properties.

As a special functional ionic liquid, chiral ionic liquids[18] is also widely studied for

both the characteristics of chiral and ionic liquids. They are found more efficient than

traditional chiral solvents in asymmetric synthesis, stereoselective polymerization

and separation of chiral substances.

1.2 Utilization of CO2

In recent years, global warming caused by atmospheric greenhouse gases

(CO2, CH4, N2O, HFCs, PFCs, SF6, etc.) has become one of the most significant

environmental problems. Carbon dioxide (CO2) is the main component of the

greenhouse gases. Since the first industrial revolution, the consumption of fossil

fuels has resulted in a rapid increase of global CO2 emissions. The global CO2

emissions have increased from 2 billion tones to over 36 billion tones since 1900 to

2015. Recent data reported that the increase of fossil CO2 emissions in 2018 is 2.7 %

(range of 1.8 % to 3.7 %) based on the Global Carbon Project. [19]

CO2 is also a very important nontoxic, abundant, natural, inexpensive and

renewable C1 building block. [20–23] Many methods and technologies are

developed for efficient capture, storage and utilization of CO2 such as Carbon

Capture Storage (CCS), Carbon Capture Utilization and Storage (CCUS) and

Carbon Capture Utilization (CCU). The utilization of CO2 as raw materials for

production of energy carriers and chemicals (such as formic acid, urea, methanol,

methane, dimethyl ether, carbonates, carbamates, carboxylic acids, ureas and ring

compounds etc.) is a promising alternative, which can reduce greenhouse gas thus

alleviate the impact of climate change, whilst producing various organic chemical

commodities. Therefore, the development utilization of CO2 has always been a hot

14 | P a g e

topic not only in academic but also international industry.[24–26] With the

intensifying of global warming effect and energy crisis, the using of CO2 as a starting

C1 material has received more and more attentions. Therefore, the efficient

transformation of CO2 into useful organic compounds is of growing interest for

resource utilization and sustainable development.

1.3 Conversion of CO2 to cyclic carbonates

It is well known that CO2 is the highest oxidation state of C and its

thermodynamic properties are stable, which limited the utilization of CO2 as a

starting C1 material. Therefore the CO2 activation always requires high-energy

inputs,[27] such as electrolytic reduction processes, high reaction temperature or

high pressure. Hence, only a small number of chemical pathways for utilization of

CO2 are developed. One of the typical feasible routes is the synthesis of five-

membered cyclic carbonates by cycloaddition of CO2 with epoxides.[28–32] This

cycloaddition reaction is a typical "atomic economy" and "green chemistry" reaction,

and as one of a few successfully industrial products that efficiently utilize CO2 as a

carbon feedstock, cyclic carbonate can be wildly used as excellent solvent in

chemical processes,[33–35] electrolyte components in lithium batteries,[36] useful

monomers for acyclic carbamates[37,38] and carbonates,[39] and intermediates in

the production of fine chemicals, etc. [40,41] There is a large demand of cyclic

carbonates with the developing technology of lithium batteries, carbonates and

dimethyl carbonate, etc. Therefore, the synthesis of cyclic carbonate is a hotspot

that widely studied and has been received more and more attention in recent

decades.

1.3.1 Routes to synthesis cyclic carbonates

There are many routes to synthesis cyclic carbonate, the earliest industrial

production of cyclic carbonate is the phosgene method[42] (Figure 1. 2). The

products can be obtained by reaction of ethylene glycol with phosgene. However,

the phosgene used to produce carbonates is highly toxic, which can cause serious

environmental pollution problems, resulting in the elimination of this old process.

Carothers first reported an ester exchanging method to synthesis cyclic carbonate

catalyzed by metal sodium or sodium methoxide.[43] The synthesis of cyclic

15 | P a g e

carbonate from the cycloaddition reaction of CO2 is quite promising and does not

result in any side products, which has obtained more and more attentions because

that this process can not only produce cyclic carbonates but also reduce

greenhouse gas. And the raw material of CO2 is cheap and easy to get. Compared

with other methods, epoxide is cheap and has high activity, the reaction conditions

of epoxide with CO2, such as temperature, pressure and catalyst are relatively easy.

Therefore, cycloaddition of CO2 with epoxide is the most important and commercial

method.

Figure 1.2 Routes to synthesis cyclic carbonates

1.3.2 Catalysts for synthesis cyclic carbonates

Catalysts are always the most critical issue for a reaction. Many catalyst

systems have been reported for the synthesis of cyclic carbonates by cycloaddition

of CO2 with epoxide. The main industrialization catalysts for the coupling of CO2 and

epoxides are alkali metal salt and quaternary ammonium salts, such as potassium

iodide (KI) and tetrabutylammonium bromide (TBAB). However, the reaction

temperature is always higher than 200 oC with CO2 pressure around 8 MPa,

catalysts need to be separated from cyclic carbonates by decompression distillation.

The harsh conditions led to a high equipment cost and increasing energy

consumption. The design of high activity catalysts has always been a research

hotspot in this field.

16 | P a g e

1.3.2.1 Metal containing catalysts

1.3.2.1.1 Metal halides and metal oxide

The metal halide is the earliest reported catalyst for the synthesis of cyclic

carbonates from epoxide and CO2. The metal halide is cheap and with high stability.

However, high temperature and high pressure are often required and results in low

yield of the products. So, some co-catalysts are always needed or used as for the

synthesis of cyclic carbonates. For example, Han et al.[44] reported potassium

halide (KCl, KBr, and KI) in the presence of β-cyclodextrin (β-CD) as a catalyst for

the coupling of CO2 with propylene oxide (PO) to prepare propylene carbonate (PC).

Because of synergetic effect in promoting the reactions, KI-β-CD catalytic system

showed the highest activity among all the catalysts, a 98% yield of PC could be

obtained within 4 hours under the conditions of 120 oC and 6 MPa CO2 pressure.

The catalyst remains high stability after five times recycle. Han et al. also prepared

lecithin[45] and cellulose[46] as a co-catalyst of potassium halides for the

cycloaddition of CO2 with PO to produce PC. Both catalyst systems showed a high

yield and selectivity at 100 °C and 2 MPa conditions. They reported the first

theoretical research about KI and the co-catalytic mechanism of hydroxyl

substances by density functional theory (DFT) method.[47] Werner et al.[48]

prepared a series of amino alcohols combined with KI for the coupling reaction of

CO2 and epoxides. The catalyst system triethanolamine/KI was found to be the

highest yield of cyclic carbonates because of the presence of hydroxyl groups

significantly enhances the catalytic activity. They also reported a polydibenzo-18-

crown-6 as a co-catalyst and polymeric support in combination with KI for the

cycloaddition CO2 and epoxide to cyclic carbonates, which could convert a large

number of terminal epoxides to the desired cyclic carbonates in yields up to 99 %

without any solvent.[49] Furthermore, it could be successfully reused at least 20

times with an excellent yield of 99 %. Shirakawa et al.[50] used KI/tetraethylene

glycol complex for the synthesis of cyclic carbonates from epoxides and CO2. It

showed 99% yield of products within 24 hours at the near room temperature 40 oC

and 1 bar of CO2 without any solvents. Metal halides catalyst system incombination

with a co-catalyst, such as wool powder,[51] organic base,[52–55] formic acid,[56]

N-heterocyclic compounds,[57] lignin,[58] sugarcane bagasse[59] and

17 | P a g e

phosphine[60] have also been extensively studied and exhibited high activity. Metal

oxide catalyst system was wildly studied.[61] For example, Kaneda and co-workers

reported the Mg-Al mixed oxides and used them as efficient catalysts for the

cycloaddition of CO2 with epoxides.[62] Furthermore, the catalysts were found to be

reusable.

1.3.2.1.2 Metal-organic framework

Recently, metal-organic framework (MOF) has been widely reported in trapping

and the conversion of CO2 for its porous structure high specific surface area.[63–68]

Ahn and co-workers[69] reported the utilization of Mg-MOF-74 crystals for

adsorption and conversion of CO2. The adsorption isotherms for CO2 showed 350

mg/g adsorption capacity at 298 K. Then, it was used in cycloaddition of CO2 with

styrene oxide (SO), 95% yields of products could be obtained without any co-

catalysts under reaction conditions of 2.0 MPa and 373 K. Duan group[70] prepared

a discrete singlewalled MOF nanotube based on tetraphenyl-ethylene. Then it was

used in the cycloaddition of CO2 with epoxides and showed a >99% yield of products

within 12 hours under 1 MPa of CO2 and 373 K in the present of tetrabutylammonium

bromide (TBAB). Furthermore, the turnover number (TON) and initial turnover

frequency (TOF) are 17500 and 1000 respectively. Carreon and co-workers[71]

synthesized an amine functionalized zeolitic imidazole framework-8 (ZIF-8) and

used for the producing of chloropropene carbonate (CPC) from CO2 and

epichlorohydrin. ZIF-8 displayed a 100 % conversion of epichlorohydrin high

epoxide conversions because of the high CO2 adsorption capacity of the amine

group. However, the ZIF-8 catalysts lost their distinctive crystalline structure and

catalytic activity during the recycling experiment. Park et al. reported[72] a Ni based

MOF Ni2(BDC)2(DABCO) under solvothermal conditions and used as a

heterogeneous catalyst in the chemical fixation of CO2 to epoxides. The authors

showed the best catalyst had a conversion yield of 93 % after 12 hours reaction

under 80 oC and 2 MPa CO2 with the presence of TBAB as a co-catalyst.

Ni2(BDC)2(DABCO) was reused at least for five times without any obviously loss in

the catalytic activity. Verpoort and co-workers[73] prepared a bimetallic Zn/Co-ZIF

catalyst for conversion of CO2 with epichlorohydrin to CPC. The catalyst showed

93 % yields of CPC within 8 hours under 140 oC and 8 bar of CO2 pressures for

presence of acid and basic sites. Furthermore, the magnetic characteristics of the

18 | P a g e

catalyst resulted in the easily separation of catalyst from products by using a magnet,

and the catalyst could be reused for at least eleven cycles.

1.3.2.1.3 Metal porphyrins

Ema et al[74] synthesized a series of bifunctional porphyrin catalysts.

Subsequently, they were found to be excellent catalysts for the coupling reaction of

CO2 with epoxides to produce cyclic carbonates. The magnesium catalyst showed

a turnover frequency (TOF) and turnover number (TON) of 46 000 h-1and 220 000,

and zinc catalyst showed a TOF and TON 40000 h-1 and 310000 because of the

multiple catalytic sites activate the epoxide. In the same year,[75] they also reported

bifunctional MgII porphyrin catalysts with Br−, Cl−, and I− for synthesis of cyclic

carbonates from CO2 and epoxides without any solvent. The best catalyst showed

a TOF and TON 19000 h-1 and 138000 separately caused by cooperative action of

the MgII and Br− and a conformational change of the quaternary ammonium cation.

Furthermore, the mechanism was demonstrated by Density functional theory (DFT)

studies. Ding and co-workers[76] supported a magnesium porphyrin and

phosphonium salt onto porous organic polymer (Mg-por/pho@POP) and used as a

heterogeneous catalyst for conversion of CO2 to cyclic carbonate. This catalyst

showed the highest activity of a heterogeneous catalyst with a TOF up to 15600 h−1.

Jing et al[77] synthesised a series of bisimidazole-functionalized porphyrin cobalt

(III) complexes. They were found good solvent-free homogeneous catalysts for the

production of cyclic carbonates via cycloaddition of CO2 to epoxides and showed

99.0 % yield of CPC under the conditions 120 °C and 2.0 MPa of CO2 for 6 hours.

Furthermore, this catalyst could also be used at 1 bar of CO2.

1.3.2.1.4 Metal (salen) or metal (salphen) complex

Metal complex such as salen, salophen, and related ligands have been widely

reported in the cycloaddition of CO2 with epoxides to form cyclic carbonates as the

easily design and highly tunable structure.[78] Based on the different metal ions,

metal (salen) complex can be classified into Co(salen), Cr(salen), Zn(salen)[79] and

Al(salen) etc. Nguyen and co-workers reported chiral Co(salen) complex with

DMAP as co-catalyst for the coupling of CO2 with epoxides to afford cyclic

carbonate.[80] The conversion of propylene oxide gave good performance of cyclic

carbonate within 1.5 h at 100 oC and 2 MPa CO2 pressure in the presence of CH2Cl2.

Lu and Sun group covalent a series of nucleophilic groups to Cr(salen)

19 | P a g e

complexes.[81] The authors found 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene

(MTBD) functionalized Co(salen) complex was the best catalyst, and could show an

initial TOF 1936 h-1 for the conversion of propylene epoxide (PO) within 1 hour. 97 %

yield of propylene carbonate (PC) could be obtained after 8 hours. The best catalyst

displayed good activity even at room temperature and 0.5 MPa CO2 pressure.

Interestingly, the binary system composed of Cr(salen) complex with MTBD as co-

catalyst was completely inactive at the same conditions. Kleij and co-workers

reported a bunch of Zn(salphen) complexes with TBAI as a co-catalyst for the

cycloaddition of CO2 with epoxides to produce cyclic carbonates.[82,83] Most of the

catalyst systems showed high activity, and the mechanism was also demonstrated

by DFT study. Lu group reported Al(salen) complex combined with TBAB as a co-

catalyst for the coupling of CO2 with epoxide.[84] It showed a catalytic TOF of 3070

h-1. Besides the metal(salen) complex, “Non-Salen” metal complex, such as

transition metal-based complex,[85] and schiff base complex[86,87] were also

widely studied in the cycloaddition reaction of CO2 with epoxide.

1.3.2.2 Organic base catalyst

Organic base is cheap and has diverse structures. It is reported for the fixation

of CO2 with epoxides for its property of absorption and activation of CO2.[88] Such

as organic amine, [89] pyridine,[90] DBU,[53,91] 1,5,7-triazabicyclo[4.4.0]dec-5-ene

(TBD),[92] schiff bases[93] and tetramethyl guanidine (TMG)[94] etc. (Figure 1. 3).

Figure 1.3 Structures of organic base catalysts

However, the activity of organic base catalyst is low, because they can only

20 | P a g e

activate CO2 but not epoxide.[89] The hydrogen bond donor (HBD) is widely used

to activate epoxides by forming the hydrogen bond interaction with epoxides, which

can highly promote the cycloaddition reaction. To improve the catalytic activity of

organic bases, researchers use the synergistic catalytic effect of organic bases and

HBD to form a binary catalytic system for catalyzing the synthesis of cyclic

carbonates from CO2 and epoxides. Reported HBDs include phenol and its

derivatives,[95] boric acid,[96] alkanol amines, cellulose,[97,98] P-cyclodextrin (P-

CD),[99] amino acids[100] and water,[101,102] etc. Shi and co-workers

reported[103] a series of organic bases, such as DMAP, DBU, 1,4-

diazabicyclo[2.2.2]octane (DABCO), triethylamine and pyridine, in combination with

phenol as binary catalyst system to catalyse the cycloaddition reaction. It was found

that the addition of phenol could significantly increase the catalytic activity, and the

DMAP/p-methoxyphenol have been proved to be the most efficient catalyst system,

98 % yield of PC could be achieved under 120 oC and 3.57 MPa of CO2 pressure

after 48 hours reaction. Park et al[100] used a binary catalytic system of naturally

occurring a-amino acids (AAs)/H2O for producing propylene carbonate (PC) from

propylene oxide (PO) and CO2. It was found L-His/H2O system showed highest

yield of PC from coupling of CO2 and PO under CO2 pressure 1.2 MPa and 120 oC

after 3 hours. Roshan et al.[104] studied the effect of water for the organic base

catalyst system. It was found that the addition of water can significantly increase the

catalytic activity of organic bases such as pyridine, imidazole, DMAP, etc. DFT

calculation studies demonstrated that the in situ generated bicarbonate in the water-

CO2-base system were the main active sites, rather than carbamates or hydroxyl

groups.

Zhang group[105] studied the use of binary catalytic system consisting of DBU

and biomass material cellulose. This catalyst system can both activate epoxide and

CO2 by hydrogen interaction of cellulose-epoxide and DBU adsorption of CO2.

Furthermore, DBU can also play the role of a nucleophilic group and promote the

ring opening process of epoxide. The possible catalytic reaction mechanism is

shown in Figure 1.4. The conversion of PO reached 93% within 2 hours at the

optimized reaction conditions of 120 ° C and 2 MPa of CO2. In addition, the catalyst

could be reused with high activity and selectivity.

21 | P a g e

Figure 1.4 The mechanism for the DBU–cellulose catalysed reaction. [105]

1.3.2.3 Ionic liquids catalyst

Ionic liquids catalyst is a kind of organic salt that composed of organic cations

and organic/inorganic anions. In recently, researchers pay more and more

attentions on ionic liquids catalysts for the cycloaddition reaction of CO2 and epoxide

because of its unique properties. Ionic liquids can play the role of both solvent and

catalyst, and the structure can be easily designed and synthesized. To date, a wide

range of ionic liquids catalysts for this reaction have been developed, such as

imidazolium based ILs,[106–109] pyridine based ILs,[12,110] ammonium based

ILs,[111–113] phosphonium based ILs,[105,114–116] organic amines based

ILs,[117–119] metal based ILs,[120–122] supported ILs[68,112,120,123–127]and

poly ILs[128–130] etc.

1.3.2.3.1 Imidazole based ionic liquids

Imidazole based ionic liquid is most reported ionic liquids and have been widely

studied. Deng et al.[131] first reported the use of ionic liquid for catalysing the

cycloaddition reaction of CO2 with epoxide at 2.5 MPa and l10 oC. The catalytic

activity of different ionic liquids was studied. Kawanami et al.[132] investigated the

effect of the side chain length of the imidazolyl ionic liquid on the catalytic activity of

cycloaddition of CO2 with epoxide. The results showed that the longer the carbon

chain had a positive effect on the catalytic effect. The reason might be that the longer

carbon chain will have weaker electrostatic interaction of the anion and cation, and

22 | P a g e

led to the increasing nucleophilicity of the anion. Numerous studies have reported

that the binary catalyst system ionic liquids/metal halides had a high activity.[133]

For example, ZnCl2/[bmim]Br catalyst system reported by Xiao et al.[134] had

excellent activity for the cycloaddition reaction. Promising yield of products could be

obtained under the optimized conditions of 100 oC and 1.5 Mpa of CO2 pressure.

The TOF could reach to 5410 h-1.

Figure 1.5 The mechanism of cycloaddition of CO2 with epoxides by HEMIMB[107]

With the development of ionic liquids, some HBD functionalized ILs are

designed and exhibit excellent catalytic effects than conventional ILs because of the

activation of epoxide by HBD. In recent years, many ionic liquids functionalized with

hydroxyl, carboxyl and amino groups have been widely reported. Zhang et al.[107]

first reported the use of hydroxyl functionalized imidazolium ionic liquids to catalyse

the synthesis of cyclic carbonates by coupling reaction of CO2 and epoxide. The 1-

(2-hydroxyethyl)-3-methylcarbazole bromide (HEMIMB) was found to be the best

catalyst, and 99 % yield and selectivity of PC could be obtained within 1 hour under

the optimized reaction conditions of 125 oC and 2.0 MPa of CO2. The hydrogen bond

interaction between hydroxyl group and epoxide resulted in the polarizing of the C-

O bond and made the ring-open of epoxied easier. The catalytic mechanism was

shown in Figure 1.5. Cokoja et al.[109] synthesized hydroxy-functionalized mono-

and bisimidazolium bromides catalysts for the cycloaddition of CO2 and epoxides.

23 | P a g e

The most active catalyst showed a high conversion at 70 oC and 0.4 MPa CO2).

1.3.2.3.2 Ammonium based ionic liquids

Some of the quaternary ammonium salts have been industrialized. Calo et

al.[135] first discovered that molten quaternary ammonium salts such as TBAB or

TBAI can be used as both solvent and catalyst to catalyse the coupling reaction of

CO2 with styrene oxide (SO) to synthesize cyclic carbonate. 83 % yield of styrene

carbonate (SC) could be obtained under at 120 oC. Lu et al found that the

tetradentate Schiff base aluminum complex (SalenAlCl) and quaternary ammonium

salt could efficiently catalyse the reaction of CO2 with epoxide to prepare cyclic

carbonate. North[136] proposed a new catalytic cycle that fully explains the role of

the tetraalkylammonium bromide co-catalyst.

1.3.2.3.3 Pyridine based ionic liquids

Zhang et al.111 reported a series of carboxyl functionalized ionic liquids as acid-

base bifunctional catalysts for catalysing the reaction. Authors believed that the

enhancement of hydrogen bonding will restrict the activity of anions, thus will

weaken the nucleophilicity and led to the decreasing of catalytic activity.

1.3.2.3.4 Protic ionic liquid

Protic ionic liquid (PILs) that synthesized by acid-base neutralization reaction,

which can provide a proton to form a hydrogen bond with the oxygen atom of the

epoxide, thus being an ideal catalyst for the cycloaddition of CO2 with epoxide to

produce cycli carbonate. He et al.[137] synthesized a series of PILs and used for

this cycloaddition reaction. DBU hydrochloride ([DBUH]C1) was found to be the best

catalyst and showed 97 % yield of PC within 2 hours under 140 oC and 1 MPa CO2.

The catalyst could be recovered by distillation under reduced pressure and reused

at least 6 times without obvious loss of catalytic activity. Tassaing et al.[138]

synthesized a series of TBD based PILs TBDHX and used for this reaction. The

effect of different anions was investigated, TBDHBr was found to be the best catalyst.

Furthermore, DFT calculation was conducted and the results showed that hydrogen

bond interaction between TBDH and PO could reduce the energy of the epoxide

ring-opening process, thereby accelerating the reaction.

1.3.2.3.5 Supported ionic liquid

Homogeneous ionic liquids generally have high catalytic activity. However,

distillation under vacuum conditions is required for the separation and recycling of

24 | P a g e

most homogeneous ionic liquids. This is normally a highly energy-consuming

process. Heterogenization of homogeneous catalysts is an effective method to

facilitate the recycling of the catalyst. Support ionic liquids onto a certain carrier is

an efficient way to heterogenization of homogeneous catalyst, therefor the

separation of supported ionic liquids and the products can be realized by simply

filtration. Takahashi et al.[139] first reported the immobilization of quaternary

phosphonium ionic liquids on silica. The catalytic activity of this catalyst was greatly

improved compared with homogeneous quaternary phosphonium salts due to the

synergistic effect silica and epoxide. Zhang et al.[140] reported a chitosan-

supported ILs to catalyse the cycloaddition reaction of CO2 into epoxide. The

catalyst can activate both epoxide and CO2 by hydroxyl groups in chitosan and

tertiary amines. Furthermore, the catalysts can be recycled five times without loss

of activity. Park et al. grafted a carboxyl functionalized imidazolyl ionic liquid onto

silica gel (CILX-Si) which, and used as a heterogeneous catalyst for the synthesis

of cyclic carbonate from CO2 and epoxide.[141] The synergistic effect of COOH and

halogen anions could promote the catalytic activity, and the catalyst could be

recovered by simple filtration.

Figure 1.6 Mesoporous silic supported ionic liquids[142]

Zhang group[142] synthesized mesoporous silica (mSiO2) based ILs for the

cycloaddition of CO2 with epoxide to cyclic carbonates. The catalyst showed

excellent catalytic because of the larger proportion of mesoporous. XPS analysis

and DFT calculation were conducted to study the good recyclability of this catalyst

(Figure 1.6).

25 | P a g e

1.3.2.3.6 Polymeric ionic liquids

Synthesis of polymeric IL catalysts by polymerization of the double bond is an

interesting topic. The unique advantage of the highly cross-linked polymeric ILs

catalyst made it a high efficient heterogeneous catalyst for the conversion of CO2 to

cyclic carbonate. [129] Han group[143] first reported the use of a highly cross-linked

polymer-supported IL (PSIL). The catalytic activity of the PSIL for the producing of

PC from CO2 and epoxides were investigated. The results showed that nearly all

the PO could be converted to PC within 7 h under 6 MPa CO2 and 383 K. The PSIL

could be easily separated from the products and reused. He and Sakakura[128]

synthesized a poly phosphonium ILs by covalenting bound phosphonium chloride

to the fluorous polymer. The catalyst was conducted as a homogeneous CO2-

soluble catalyst for producing of cyclic carbonates from CO2 and epoxide under

supercritical CO2 conditions. 95 % yield of PC was obtained at 150 oC and 8 MPa

after 8 hours reaction. The catalyst could be recovered by filtration. High activity and

selectivity were achieved after reused 7 times.

Figure 1.7 Synthesis of PILs in this study. [144]

Zhang et.al[144] prepared a series of hydroxyl-functionalized poly(ionic liquids)

(PILs) and used for the synthesis of cyclic carbonates via cycloaddition of CO2 and

epoxides (Figure 1.7). Because of synergetic effect on promoting the reaction by the

hydroxyl and bromide anion, the best PILs displayed a 99% yield and 100%

selectivity of PC within 4 hours under 130 oC and 2.5 MPa of CO2 pressure with a

26 | P a g e

catalyst loading of 1.0 mol%.

Figure 1.8 Structure of DFP[145]

Zhang group[145] also reported a dicyandiamide–formaldehyde polymer (DFP)

based polyquaternium ILs and employed for cycloaddition of CO2 with epoxides

(Figure 1.8). Structure was shown in Figure 1.8. The authors found that the

ammonium bromide modified polyquaternium ILs (ABMDFP) was the optimal

catalyst, and 99 % yield and 99 %selectivity of PC could be obtained within 3.5 hour

under the optimal reaction conditions of 130 °C and 2.0 MPa of CO2 with a catalyst

loading of 2.0 mol%. The catalyst could be easily recovered by filtration and reused

six times with only a slight loss of catalytic activity.

Figure 1.9 General route for the synthesis of carboxyl functionalized phosphonium-based

PIL[146]

27 | P a g e

In year of 2017, Zhang group[146] synthesized phosphonium-based polymeric

ionic liquids (PILs) by microfluidic technique (Figure 1.9). The average diameter

sizes of the particles could be turned from 6.4 to 375 nm. They are successfully

conducted in the cycloaddition of CO2 with epoxides to form cyclic carbonate. The

best catalyst displayed 99 % yield of PC after 4 hours at 150 oC and 2 MPa of CO2.

Authors demonstrated that carboxylic acid group could activate the ring-opening of

epoxide by in situ FTIR.

1.3.3 Cycloaddition of CO2 and epoxide under mild conditions

Although most of the catalyst systems show a good yield to produce carbonates,

high temperatures (>100 °C) and/or high CO2 pressures, are always needed. Such

reaction conditions not only increase energy consumption and require specific

equipment, but also raise certain operational risks. Hence, great efforts have been

focused on the development of efficient and sustainable catalyst systems that can

be carried out chemically converting CO2 at relatively mild reaction conditions. In

this respect, many catalysts have been synthesized and exhibited good

performance in the synthesis of cyclic carbonates from CO2. For example,

metal−based catalysts, such as metal(salen), MOF, metal porphyrin were reported

to have a good yield of cyclic carbonates at atmospheric pressure and/or room

temperature because of its multi-activity sites consisting of metal ions and halide

ions. In this respect, North group made great contributions. North and co-workers

reported an Cr(III) salphen complexes for the cycloaddition reaction under ambient

conditions with the presence of TBAB (tetrabutylammonium bromide).[147] The

catalyst system could catalyse the cycloaddition of CO2 to various terminal epoxides

under ambient conditions. It was found that both the catalyst and co-catalyst played

an important role in this reaction via interacting with epoxide to form an intermediate

complex. In the same year, North et al. reported[147] a chromium-based complex

functionalized with amino groups. The amino-functionalized Cr(III)(salen) complex

showed similar results with Cr(III)(salophen) complexes. The group of He

reported[148] a bunch of bifunctional Zn(salen) complexes composed by multiple

HBD and ammonium bromides groups for coupling of CO2 with styrene oxide to

produce 4-phenyl-1,3-dioxolan-2-one. Due to the synergistic effects of HBD on

epoxide activation, the best catalyst could show 90 % yield of product within 12

28 | P a g e

hours under 120 oC and 0.1 MPa CO2 without any co-catalysts. However, these

catalysts need the aid of DMF as a solvent. Ma et al.[149] reported a nbo MOF

composed by Lewis active sites and metal Cu for this coupling of CO2. MMCF-2

[Cu2(Cu-tactmb)(H2O)3(NO3)2] was found to be the best catalyst, and 95.4 % yield

of PC could be obtained after 48 hours reaction under room temperature and 1 atm

CO2 with the presence of Bu4NBr as a co-catalyst. Jiang et al.[150] reported the

integration of photothermal effect of carbon-based Zn-MIF materials for the

cycloaddition of CO2 with epoxide. The best catalyst showed 94 % yield of cyclic

carbonate after 10 hours with the presence of TBAB as co-catalyst and DMF as

solvent under 1 bar CO2, 300 mW·cm-2 full-spectrum irradiation and ambient

temperature. Furthermore, catalytic activity of this catalyst system would decrease

sharply to < 5 % and 14 % without co-catalyst or light irradiation respectively.

Authors also studied conversion of a mixture gas (0.15 bar CO2, 0.85 bar N2) at the

same conditions. This catalyst system displayed 90 % yield of cyclic carbonate when

the reaction time was extended to 30 hours. This work is the first report on

integration of photothermal effect for the cycloaddition of CO2 with epoxide to

produce cyclic carbonate. Other metal based catalysts system, such as dual-walled

cage MOF,[151] diphenylporphyrin]manganese(III) chloride (DPP-

MnCl)/phenyltrimethylammonium tribromide (PTAT),[152] metal porphyrin based

porous organic polymer (POP-TPP)/TBAB,[153] bisimidazole-functionalized

porphyrin cobalt(III) complexes[154] were also reported for the cycloaddition of CO2

to produce cyclic carbonate under mild conditions, and showed promising catalytic

activities.

Binary catalyst systems, such as organic base/HBD and organic base/ metal

halides were widely reported due to the activation of epoxides by a nucleophile and

a strong hydrogen bond or activation of CO2. Hirose and co-workers[155] reported

the use of pyridine methanol as HBD associated with TBAI as a binary system for

the cycloaddition reaction of epoxide and CO2 to produce cyclic carbonates. A series

of HBD was studied, and 2-pyridinemethanol was found to be the best HBD with

TBAI, showed 92 % yield of CPC within 24 hours under room temperature (25 oC)

and 1 bar CO2 (balloon). Interestingly, optically pure epoxides could be forming the

corresponding products with minimal loss in the ee values. Wang and co-workers[96]

investigated a series of boronic acids as HBD combined with TBAI for the coupling

29 | P a g e

of CO2 with epoxides into produce cyclic carbonates in different solvents under mild

conditions. In this study, H2O was found to be the optimal solvent. The best boronic

acide/TBAI system could show 90 % yield and 90 % selectivity of corresponding

cyclic carbonate within 4 hours under 50 oC and 1 MPa CO2 in H2O. Moreover, the

products would automatically separate from the mixture reaction system after the

reaction. Authors investigated the recycling experiment by using a polystyrene

supported boronic acid. The result showed that the boronic acid could be used at

least 8 times without any obvious loss of catalytic activity. Hirose et al.[88] also

studied the use of a serious organic base combined with TBAC as a binary system

for the coupling of CO2 with epoxide to produce cyclic carbonates. A bunch of

organic bases was studied, such as DBU, DMAP, pyridine etc. DBU/TBAC was

found to be the best catalyst system and showed 96 % yield of cyclohexene oxide

within 20 hours under 120 oC and 1atm CO2. The binary system of benzyl bromide

combined with organic base catalyst system was also reported by Hirose group, and

showed high activity at mild conditions of 25 -65 oC and 1 atm CO2.[156] Recently,

Werner et al.[157] reported a CaI/crown ethers catalyst system for the synthesis of

internal and trisubstituted cyclic carbonates from bio-derived epoxides and CO2. The

best catalyst can catalytic various internal epoxides to the respective carbonate with

isolated yields up to 98 % within 24 hours at only 45 °C, 0.5 MPa CO2 pressure with

a catalyst loading of 5 mol. Binary systems, such as MgBr/Phosphine,[60]

DBU/CaBr,[53] DBU/ascorbic acid[91] etc. were also reported for the coupling of

CO2 to produce cyclic carbonate under mild conditions, and showed promising

catalytic activities.

Recently, most studies have focused on organocatalyst, especially ionic

liquids.[30,158–161] Dyson and co-workers[162] studied the roles of the ring protons

of imidazolium salts in the cycloaddition of CO2 with epoxides to produce cyclic

carbonate catalysed by imidazolium and related salts. The results demonstrated that,

the nucleophilicity of the anion played the key role in the overall activity, as

stabilization of intermediates by C2, C4, or C5 protons in imidazolium salts took

place. Therefore, the reactivity of the halide anion strongly depends on the nature

of the cation and cosolvents. Wang and co-workers[163] reported a dual hydroxyl

functional mesoporous poly(ionic liquid)s as recyclable heterogeneous catalysts for

the cycloaddition of epoxides with CO2 under mild conditions. The best catalyst

30 | P a g e

showed 99.4 % yield of CPC at 0.1 MPa CO2 and 70 oC after 48 hours reaction.

Furthermore, it could be easily recovered and reused with stable activity. Ma et

al.[164] reported that the use of porous ionic polymer as heterogeneous for capture

of CO2 and catalyse CO2 to form cyclic carbonate. The polymer could chemically

fixation CO2 with epoxide to cyclic carbonate under mild conditions due to the porous

nanostructure and large surface area. The catalytic activity was even higher than its

corresponding homogeneous quaternary salt catalyst. Similarly, mesoporous-

macroporous layered poly ionic liquids with an adjustable pore structure and highly

dense catalytic active site was reported by Wang and Zhou et al.[165] to catalyse

the conversion of CO2 to cyclic carbonate under 0.1 MPa CO2 and mild temperature.

The catalyst exhibited a high yield (>99%) and allowed recycling of the IL solvent.

Most recently studies have been focused on protic ionic liquids (PILs), which

exhibited not only excellent ability of reversible CO2 capture but also highly efficient

CO2 chemical conversion even under ambient conditions since the powerful H-

bonding.[166–168] Han et al[169] employed a novel dual-ionic liquid system for

cycloaddition of epoxides with CO2 under temperature from 30 to 60 °C at 1 atm,

the results showed 95 % yield of CPC could be obtained after 20 hours at 30 oC and

1 atm CO2 without any solvents. Zhang et al.[170] synthesized a bunch of protic

ionic liquids for the conversion of CO2 with styrene oxide (SO) to Styrene Carbonate

(SC) at mild conditions. They found 4-(dimethylamino) pyridine hydrobromide

([DMAPH]Br) showed highest catalytic activity, 96 % yield of SC could be obtained

after 4 hours with a catalyst loading of 1 % under 120 oC and 1 atm. Furthermore,

authors studied the conversion of flue gas (mixture of 15% CO2 and 85% N2) with

SC. The best catalyst displayed 92 % yield within 14 hours under the same reaction

conditions. Shirakawa et al.[171] reported the use of a protic triethylamine

hydroiodide as an effective one-component catalyst for the coupling of CO2 with

epoxide at 40 °C under ambient pressure. However, the catalytic activity decreased

obviously during the recycling experiment because the partial loss of the catalyst for

the sublimation property under the distillation conditions. PILs such as pyrazolium

based PILs,[172] imidazole and pyridine based PILs[173] were also reported for the

coupling of CO2 with epoxide to form cyclic carbonate under mild conditions, and

they all showed excellent catalytic activities at this mild conditions.

31 | P a g e

1.4 Research contents

Although some of the catalyst systems show a good yield to produce

carbonates, even at mild conditions, unsatisfactory activities of large catalyst loading

and long reaction time (>24h) compared to high temperature and pressure, the

presence of metals and/or toxic solvents are still drawbacks that need to overcome.

Therefore, the design of efficient, green and metal-free catalysts is still a great

challenge toward effective CO2 conversion under mild conditions. For energy

efficient reasons, we designed a series of functional ILs and used them for

catalysing the cycloaddition reaction of CO2 with epoxides under mild conditions.

The major work and results for this dissertation are summarized as follows:

1 A series of carboxylic acid-based functional ionic liquids (CABFILs) were

facilely prepared by a one-step synthesis method. They displayed reversible

temperature-controlled phase transitions in PC, which were useful for the coupling

reaction and separation processes. CABFILs were successfully used in

reaction−separation for conversion of CO2 to carbonates under metal-free and

solvent-free conditions. Besides, IL 3a displayed high activity, and nearly 92% PC

yield was obtained within 20 min and could be readily separated by filtration at room

temperature for easy recycling. This approach helps to avoid further waste of the

subsequent separation step, as well as a highly effective way to combine the

benefits of heterogeneous and homogeneous catalysts, which is of great interest

from the viewpoint of energy savings and chemical engineering.

2. An efficient 1,8-diazabicyclo- [5.4.0] undec-7-ene (DBU) based bifunctional

protic ionic liquids (DBPILs) was easily prepared by acid-base reaction at room

temperature. DBPILs that composed by alkoxy anion, protic acid and nucleophilic

groups exhibited high activity for the coupling reaction of CO2 and epoxide under

mild conditions. As a metal free catalyst, the best DBPILs showed a 92 % yield of

products within 6 hours at 30 oC and 1bar CO2 without any solvents and co-catalysts.

And it could afford carbonates in good yields with broad epoxide substrate scope

and CO2 from simulated flue gas (15% CO2/85% N2).

3. DBU based ionic liquids containing aluminium (DILA) catalyst was

synthesized based on dissociating feature of proton from DBPILs. DILA was used

as a single-component and solvent-free catalyst for the conversion of CO2 to cyclic

carbonates with epoxide at mild conditions. DILA showed a catalytic activity of 96%

32 | P a g e

within 6 h in catalysing the reactions of CO2 with epoxides at 30 oC and 1 bar CO2,

because of the efficiently activating epoxides. The effect parameters such as

temperature, reaction time and catalyst dose were investigated.

4. A series of cross-linked poly (ILs) membranes (CPILM) were prepared and

used as highly efficient heterogeneous catalysts for fixation of CO2 with epoxide at

mild conditions. CPILM could show comparable activities in the coupling of epoxide

and CO2 with the traditional homogenous catalysts, because of the activity of CO2

and “homogenous-surroundings” caused by swellable properties. Swelling

behaviour was studied and found to be consistent with the experimental results of

the catalytic activity. The dependence of conversion yield on catalyst dose, reaction

temperature and time were investigated. The best CPILM could show a 90% yield

of carbonate within 24 hours at 50oC and 1 bar of CO2.

5. A series of metalloporphyrin ionic liquids (MPILs) that combine the

advantages of ionic liquid and porphyrin were designed and synthesized by one step

method. The structure and surface appearance of these BPILs were investigated.

These BPILs catalysts have multiple active sites and a good capacity of visible light

absorption due to the advantages of functional ionic liquids and metal porphyrin part,

thus can greatly reduce the energy inputs by using the visible light. They were

successfully used as a photocatalyst in cycloaddition reaction of CO2 with epoxide

to produce carbonate at 1 bar pressure under irradiation of a visible light.

33 | P a g e

Chapter 2: Temperature-Controlled Reaction-Separation

for Conversion of CO2 to Carbonates with Functional

Ionic Liquids Catalyst

2.1 Introduction

The combination of activity and recovery of homogeneous catalysts is

recognized as a great challenge in catalysis research from an industrial point of

view.[174] The reported homogeneous catalysts are usually more efficient, while it

is costly to reclaim them from reaction products. By contrast, heterogeneous

catalysts can be easily separated from the products and reused. But they are

inefficient, on the same time, the high temperatures and pressures are often

demanded, which make them practically excess costs. This has promoted the

development of efficient strategies for homogeneous catalysis and heterogeneous

separation.[175,176] Recently, Wang et al. [177] has reported the interesting finding

- the reversible liquid–liquid phase transition of IL-H2O systems by

bubbling/removing CO2. These unique IL-H2O systems are successfully used for

facile one-step synthesis of Au porous films. The group of Xiong[178] has prepared

IL-based cross-linked polymeric nanogels (CLPNs) and find that they display

reversible, temperature-driven nanoge-macrogel transitions in methanol. The

reversible phase transition phenomenon supplied a novel strategy for the efficient

combining of activity and recovery of homogeneous catalysts.

The efficient utilization of carbon dioxide (CO2) also remains the important issue,

as these may reduce the greenhouse gas and produce various organic chemical

commodities. [179–182] One of the typical viable routes is the synthesis of five-

membered cyclic carbonates via the cycloaddition of CO2 with epoxides.[183–185]

Cyclic carbonates can be extensively used as polar aprotic solvents, raw materials,

and intermediates in the synthesis of pharmaceuticals and fine chemicals,[186–188]

which made this process very attractive and important.

To this end, various catalysts have been developed.[189–194] Ionic liquids (ILs)

have been demonstrated efficient homogeneous catalysts for the synthesis of cyclic

carbonates.[132] Many functional ILs containing a Lewis acid and a nucleophile

34 | P a g e

have been reported. Cokoja group[195] synthesized hydroxy-functionalized mono-

and bisimidazolium bromides catalysts for the cycloaddition of CO2 and epoxides.

The most active catalyst showed a high conversion at very mild reaction conditions

(70 oC, 0.4 MPa CO2). Han et al.[196] prepared carboxylic acid groups-

functionalized ammonium salts for the fixation of CO2. North[197] proposed a new

catalytic cycle that fully explains the role of the tetraalkylammonium bromide co-

catalyst. Park et al.[141] exploited carboxyl-group-functionalized imidazolium-based

ionic liquids (CILs) and grafted onto silica gel for cycloaddition of CO2. Zhang et

al.[198] provide a boronic acids/onium salts system as efficient organocatalysts for

the conversion of CO2 with epoxides in H2O under mild conditions. We also reported

four kinds of carboxylic acid–base bifunctional catalysts (ABBCs) for the reaction of

epoxides with CO2.[199] Although, the reported homogeneous systems provide

higher activity, it is often inconvenient for separation. Based on the problems in

homogeneous catalytic processes, some heterogeneous catalysts have been

developed for the CO2 chemical conversion. In contrast, heterogeneous systems

are easier to separate, but they are inefficient (The most efficient metal-free

heterogeneous catalysts turnover frequencies (TOFs) are 90 h−1)[200] and hard

reaction conditions are always needed. Hence, it is highly necessary to explore a

convenient approach to realize both high activity and quick separation of catalysts.

Figure 2.1 Photograph showing the temperature-controlled phase transitions in PC (3a =

8 wt % and PC = 92 wt %).

Taking account of these issues, we exploited a series of carboxylic acid–based

functional ILs (CABFILs) as single-component, metal-free homogeneous catalysts

for cycloaddition of CO2 with epoxides into cyclic carbonates. Interestingly, this type

35 | P a g e

of ILs displayed temperature-dependent phase transitions in propylene carbonate

(PC) by controlling the chain length of carboxyl group. Thus, these catalysts offered

an efficient way to recover the homogeneous catalysts. When the catalysts were

added into PC, such a liquid/solid phase remained separated at room temperature

(Figure 2.1 step a). When heated, they readily dissolved in PC (Figure 2.1 step b),

where they could react effectively. As the mixture got cooled, the solubility of

CABFILs in PC dramatically decreased. On the same time, the catalysts precipitated

spontaneously, and the phases were separated again (Figure 2.1). So, we could

simply filtrate to recover the catalysts precipitated from the products. Besides, the

optimal ILs displayed high productivity and stability because of the activation of

epoxide and CO2. Nearly 92% PC yield and 99% PC selectivity were obtained within

20 min under metal-free and solvent-free conditions (TOFs=276 h−1). Such a

temperature-dependent dissolution-precipitation transitions behaviour helped to

avoid further waste of the subsequent separation step, which could be used to

realize the coupling of reaction and separation in energy saving and industrial

application.

2.2 General information

Carbon dioxide was supplied by Beijing Analytical Instrument Factory with a

purity of 99.95%. 1,2-Epoxyoctane, Styrene oxide and cyclohexene oxide were

purchased from Alfa Aesar-A Johnson Matthey Company, (R)-2-Oxiranylanisole, 4-

Dimethylaminopyridine, Bromoacetic acid, 3-Bromopropionic acid and 4-

Bromobutyric acid were bought from Aladdin Reagent Co. Other reagents and

chemicals (analytic grade) were bought from Sinopharm Chemical Reagent Co., Ltd,

and were used without further purification. GC-MS were measured on a Finnigan

HP G1800 A. GC analyses were performed on an Agilent GC-6890 equipped with

a capillary column (DB-624, 30 m×0.32 μm) using a flame ionization detector. NMR

spectra were recorded on a Bruker 300 or Varian 400 spectrometer. All calculations

were carried out by the use of the B3PW91 functional with the 6-311++G (d,p) basis

set as implemented in the Gaussian 09 program package.

app:ds:cyclohexene

app:ds:oxide

36 | P a g e

2.3 Experimental section

2.3.1 Main equipments

Gas chromatography- mass spectrometry (GC-MS): Agilent 6890N/5975B GC-

MS，

Gas chromatograph (GC): Agilent 6820 GC

Fourier transform infrared spectrometer (FT-IR): Thermo Nicolet 380

Nuclear magnetic resonance instrument：ARX400 Bruker, Switzerland

Thermogravimetric analyzer：Thermogravimetric Analyzer 2050

2.3.2 Synthesis of catalysts

Scheme 2.1 One step synthesis of catalysts in this study.

All the catalysts were synthesized by using one-step method. In a typical

reaction, 4-dimethylaminopyridine (50.00 mmol) and BrCnH2nCOOH (60.00 mmol)

were poured in sequence into a 250 mL three-necked flask and dissolved in ethyl

acetate. The mixture was stirred for 12 h at 50oC until the solid product was not

increased. After the reaction, the top phase was immediately poured out and the

residue was washed three times with ethyl acetate and then dried at 50oC for 12 h

under vacuum. The structures of these ILs were confirmed by NMR and IR

spectroscopy, no impurities were found by NMR.

2.3.3 Characterization of the catalysts

The catalysts were characterized by thermogravimetric analysis (TGA,

PERKIN-ELMER7 Series Thermal Analysis System) at a heating rate of 10oC min-

1. The morphology of the ILs was observed using a scanning electron microscope

37 | P a g e

(JEOL JSM 6700F). Fourier transform infrared (FT-IR) spectra were recorded on a

Thermo Nicolet 380 spectrophotometer with anhydrous KBr as standard (Thermo

Electron Co.). NMR spectra were recorded on a Bruker 300 or Varian 400

spectrometer in DMSO-d6. The characterizations are shown as following:

[CEDMAPy]Br (1a): Viscous solid; 1H NMR (DMSO-d6): δ 13.28 (s, 1H), 8.26

(m, 4H), 6.9 (m, 4H), 4.31 – 4.24 (m, 2H), 3.24 – 3.14 (m, 6H); 13C NMR (DMSO-

d6): δ 170.69, 157.38, 143.46, 139.49, 107.45, 39.6, 26.83.

[CPrDMAPy]Br (2a): Solid; 1H NMR (DMSO-d6): δ 12.88 (s, 1H), 8.27 (m, 4H),

6.9 (m, 4H), 4.37 (m, 2H), 3.2 – 3.15 (m, 6H), 2.90 (m, 2H); 13C NMR (DMSO-d6): δ

170.65, 156.75, 142.28, 140.17, 107.33, 52.94, 39.59, 34.26.

[CBDMAPy]Br (3a): Solid; 1H NMR (DMSO-d6): δ 13.25 (s, 1H), 8.32 (dd, J =

91.5, 6.8 Hz, 4H), 7.07 (dd, J = 82.3, 7.2 Hz, 4H), 3.35 (m, 2H), 3.20 (s, 6H), 2.57

(d, J = 67.0 Hz, 2H), 1.04 (d, J = 229.5 Hz, 2H); 13C NMR (DMSO-d6): δ 170.05,

157.43, 139.57, 107.44, 40.01, 39.59.

[CPeDMAPy]Br (4a): Solid; 1H NMR (DMSO-d6): δ 13.28 (s, 1H), 8.38 (ddd, J

= 11.3, 7.6, 2.6 Hz, 4H), 7.08 (m, 4H), 3.36 (s, 2H), 3.19 (s, 6H); 13C NMR (DMSO-

d6): δ 175.15, 157.43, 139.50, 107.46, 33.40, 30.23, 21.38.

Figure 2.2 The FT-IR spectra of 1a-4a

4000 3000 2000 1000 0

Wavenumber (cm-1)

1734[CEDMAPy]Br (1a)

[CPrDMAPy]Br (2a)

[CBDMAPy]Br (3a)

[CPeDMAPy]Br (4a)

13862930

38 | P a g e

2.3.4 1H NMR and 13C NMR of Products

4-methyl-1, 3-dioxolan-2-one (6a):

1H NMR (CDCl3, TMS, 400 MHz): 1.49 (d, J = 6.0 Hz, 3H); 4.05 (t, J = 8.8 Hz,

1H); 4.60 (t, J = 8.0 Hz, 1H); 4.86–4.94 (m, 1H); 13C NMR (CDCl3, TMS, 100.4 MHz):

18.95, 70.46, 73.51, 154.95 (C=O)

4-hexyl-1,3-dioxolan-2-one (6b):

1H NMR (CDCl3, TMS, 400 MHz): 0.84 (t, J = 13.1 Hz, 3H); 1.24–1.28 (m, 7H);

1.34 (t, J = 9.6 Hz, 1H); 1.65 (t, J = 11.7 Hz, 2H); 4.08 (t, J = 15.8 Hz, 1H); 4.53 (t,

J = 15.8 Hz, 1H); 4.74 (t, J = 6.9 Hz, 1H); 13CNMR (CDCl3, TMS, 100 MHz): 14.29,

22.52, 24.45, 28.87, 31.63, 33.44, 69.69, 77.49, 155.35 (C=O).

4-chloromethyl-1, 3-dioxolan-2-one (6c):

1H NMR (CDCl3, TMS, 400 MHz): 1.490 (d, 2H, J = 6.0 Hz); 4.05 (t, 1H, J = 8.4

Hz); 4.60 (t, 1H, J = 8.0 Hz); 4.86–4.94 (m, 1H); 13C NMR (CDCl3, TMS, 100.4 MHz):

18.95, 70.46, 73.51, 154.95 (C=O).

4-phenyl-1, 3-dioxolan-2-one (6d):

O O

O

O O

O

C6H13

39 | P a g e

1H NMR (CDCl3, TMS, 400 MHz): 4.34 (t, 1H, J = 8.4 Hz); 4.80 (t, 1H, J = 8.4

Hz); 5.68 (t, 1H, J = 8.0 Hz); 7.35–7.44 (m, 5H); 13C NMR (CDCl3, TMS, 100.4 MHz):

71.10, 77.92, 125.81, 129.12, 129.63, 135.70, 154.81 (C=O).

4-phenyloxymethyl-1, 3-dioxolan-2-one (6e):

1H NMR (CDCl3, TMS, 400 MHz): 4.15 [dd, 3J = 4.4 Hz, 2J = 10.8 Hz, 1H,

OCH2], 4.24 [dd, 3J = 3.6 Hz, 2J = 10.8 Hz, 1H, OCH2], 4.55 [dd, 3J = 8.4 Hz, 2J =

6 Hz, 1H, PhOCH2], 4.62 [t, 3J = 8.4 Hz, 1H, PhOCH2], 5.03 [m, 1H, OCH], 6.91 [d,

3J = 8.0 Hz, 2H, C6H5], 7.02 [t, 3J = 7.4 Hz, 2H, C6H5], 7.31 [t, 3J = 8.0 Hz, 2H,

C6H5]. 13C NMR (CDCl3, TMS, 100.4 MHz): 66.17, 68.84, 74.11, 114.57, 121.92,

129.62, 154.65(C=O), 157.71.

2.3.5 Procedure of the cycloaddition reaction of CO2 with

propylene oxide

The coupling reaction of carbon dioxide and epoxide was carried out in a 25 mL

stainless-steel reactor equipped with a magnetic stirrer and an automatic

temperature control system. In a typical reaction, appropriate amounts of PO and

catalyst were charged into the reactor at room temperature, Then, CO2 was added

to a suitable pressure from a reservoir tank to maintain a constant pressure. Control

the temperature within the desired range afterwards. After the reaction, the reactor

was cooled to room temperature in a water bath and remaining CO2 was vented out

slowly. The organic products were separated from the catalyst by filtration and

analysed by GC-MS and GC. Agilent 6890/5973 GC-MS was equipped with a FID

detector and a DB-wax column. The catalyst was washed with ethyl acetate three

times and dried under vacuum for the recycling experiment.

O O

O

40 | P a g e

2.3.6 Reaction equipment

Figure 2.3 Reaction equipment. 1. CO2 cylinder，2. Filter，3. Thermocouple，4.

Transformer，5. Reactor，6. Magnet，7. Blender, 8 Heater

2.4 Results and discussion

Figure 2.4 Structure and photographs of CABBILs (1a-4a)

A series of these CABFILs (Figure 2.4) were obtained through one-step

synthesis process at room temperature. Their solubility in PC at 25 oC was showed

in Figure 2.5. It could be observed that the carboxylic chain length of CABFILs had

great influence on solubility of CABFILs in PC: the solubility decreased sharply from

14.8% to 0.4% with the increase of chain length from 2 to 5 (1a-4a) at room

temperature. The possible reason for the different solubility was mainly attributed to

the effects of the different nonpolarity of CABFILs.[201]

41 | P a g e

Figure 2.5. The solubility of IL (1a-4a) in PC at 25oC (Determined by 1H NMR, see Fig

S11-S14).

Figure 2.6. The solubility of IL 3a in PC at different temperatures (Determined by

gravimetric method).

Then, 3a was used as a representative example to investigate the temperature-

0

2

4

6

8

10

12

14

16

4a3a

2a

So

lub

ilit

y (

g/1

00m

l)

Catalyst

1a

20 40 60 800

4

8

12

So

lub

ilit

y (

g/1

00

ml)

Temperature (o

C)

42 | P a g e

dependent solubility. The solubility of 3a in PC was as low as 0.27% at 10 oC and

increased obviously as the temperature went up (Figure 2.6). Hence, when 3a (8

wt%) was added into PC, such a liquid/solid mixture remained separated at room

temperature. When temperature went up, 3a readily dissolved in PC. As the mixture

was cooled to room temperature, the catalysts precipitated spontaneously, and the

phases separated again. We reasoned that the temperature-dependent solubility of

CABFILs in PC was mainly attributed to the intermolecular hydrogen bonding of the

ILs components.[202]

Then, nuclear magnetic resonance (NMR) studies were performed in order to

gain insight into the mechanism. First, tetraglyme was selected as a destroyer,

which could compete in the formation of hydrogen-bond,[203] to investigate the

intermolecular hydrogen bonding of the ILs components on the effect of the solubility.

The 1H NMR spectra of 3a with and without tetraglyme was shown in Figure 2.7,

the signal at 14.47 ppm was associated with the carboxylic proton, the signal of

carboxylic proton decreased after mixed with tetraglyme. Such a trend suggests

weakened interaction energy.[204] This was mainly because the hydrogen-bond of

O-H···O between carboxylic protons was broken. Similar result was found in C2 /C6

proton of pyridine ring, which indicated the broken of the hydrogen-bond C-H···Br-.

Figure 2.7. The 1H NMR spectrum of IL 3a with and without tetraglyme.

14 12 10 8 6 4 2

δ/ppm

C2/C6-COOH

CDCl3

3a

3a + Tetraglyme

14.47

14.10

43 | P a g e

Figure 2.8. The temperature-dependent 1H NMR spectrum of IL 3a in [D6] DMSO

Temperature-dependent NMR was shown in Figure 2.8 to provide further

evidence for the effect of the temperature on the solubility of ILs in PC. The signal

of carboxylic proton and C2 /C6 proton of pyridine ring also decreased when the

temperature increased from 30 oC to 80 oC, which may be caused by the broken of

the hydrogen-bonds O-H···O and C-H···Br-.[205]

Figure 2.9. (a) Molecular structure of 3a and the intermolecular hydrogen bonding of the

ILs components. See the APPENDICES for computational details.

44 | P a g e

The DFT calculations were shown in Figure 2.9 for further study of the

intermolecular hydrogen bonding. All calculations were carried out by the use of the

DFT functional with the 6-311++G (d, p) basis set as implemented in the Gaussian

09 program package. The result indicated that moleculars of 3a showed a tendency

to form a class of clusters with self-aggregation through hydrogen bonding network.

Of all the clusters, tetramolecular clusters was relatively more stable, and the

structure of the tetramolecular clusters was shown in Figure 2.9 (a). Four carboxyl

groups were forming tetramers that were connected by strong hydrogen bonds (O-

H···O distance of 1.572-1.656Å). Besides several C-H···Br contacts between Br-

anions and the cations can be observed, ranging from 2.36 to 2.87 Å. The hydrogen

bonds of C-H···Br led to the four moleculars aggregation and formed a

tetramolecular cluster.

Figure 2.10 Hydrogen bonding interaction between 3a and PC. See the APPENDICES for

computational details.

Strong hydrogen bonds were also found between 3a and PC with an O-H···O

distance of 1.93-1.94 Å and a C-H···O distance of 2.40-2.74 Å, respectively [Figure

2.10]. Therefore, based on the above results, a possible mechanism of reversible

temperature-dependent phase transitions behaviour of CABFILs was proposed.

The nonpolarity of CABFILs with a longer carboxylic chain was higher than those

with a shorter chain, as well as a stronger intermolecular hydrogen bonding, which

made them hardly dissolved in polar solvent PC at room temperature. When heated,

the intermolecular hydrogen-bond network of O-H···O and C-H···Br was broken.

Then, the molecular of ILs diffused into PC. Finally, the formation of hydrogen bond

between CABFILs and PC led to the dissolution of CABFILs. The dissolution

45 | P a g e

process ended as precipitation-dissolution reached equilibrium.

Figure 2.11 SEM images of the ILs 3a.

SEM images of the ILs 3a were also shown in Figure 1, and the surface profile

of 3a was like the brain wrinkle (Figure 2.11) due to the tetramolecular cluster

structure caused by the hydrogen bonding network. This particular shape could

provide increased surface area and was useful in catalytic processes.

Table 2.1. Catalysts screening for the synthesis of propylene carbonatea

Entry Catalysts PO Conv. (%)b PC Select. (%)b

1 [BPy]Br 47 99

2 [CEDMAPy]Br (1a) 89 99

3 [CPrDMAPy]Br (2a) 94 99

4 [CBDMAPy]Br (3a) 90 99

5 [CPeDMAPy]Br (4a) 89 99

6 c [CBDMAPy]Br (3a) 99 99

7 c [{(CH2)3CO2H}inic]Br111 73 96

8 c [{(CH2)3CO2H}bpy]Br111 83 99

9 [CBDMAPy]Br (3a) 99 99

10 Poly imidazolium salt 90 99

aReaction conditions: PO (14.3 mmol), catalyst (1.0 mol%), CO2 pressure (2.0 MPa), reaction

time (1.0 h) and temperature (120 oC). bConversion and selectivity were determined by GC using

biphenyl as the internal standard. cTemperature (125 oC). dPO (21.4 mmol), catalyst (60 mg),

CO2 pressure (1.0 MPa), reaction time (1.5 h), temperature (110 °C).

This unique phase behaviour and structure were much useful in the

cycloaddition reaction of CO2 with epoxides. Due to the ring-opening of epoxides

assisted by the hydrogen bond, all the CABFILs exhibited higher PC yield than the

46 | P a g e

butylpyridinium bromide ([BPy]Br) without carboxyl group (Table 2.1, entries 2-5 vs.

1). Compared with the other CABFILs, 2a was observed the highest activity.

Considering that 2a could only partly transformed to precipitate at room temperature,

3a was chosen as the optimal catalyst for further investigation. The comparison of

the catalytic activity of 3a with our previously reported acid–based bifunctional ILs

was also displayed in Table 2.1. 3a exhibited much higher activty than the

bipyridinium- and isonicotinic-based functionalized ILs (entry 6 vs. 7, 8). 3a exhibited

much higher activity than the bipyridiniumand isonicotinic-based functionalized ILs

(entry 6 vs 7, 8). We also compared catalytic activity of 3a with the most efficient

metal-free heterogeneous catalysts (TOFs = 90 h−1) at the same conditions. Then,

the reaction conditions such as influence of temperature, CO2 pressure, reaction

time and dosage of catalysts on the cycloaddition reactions of CO2 with PO were

investigated to find the most appropriate and efficient reaction conditions (Figure

2.12-2.15). The results indicated that nearly 92% yield of PC together with 99%

selectivity was obtained at 130 °C, 2.0 MPa in 20 min (TOFs = 276 h−1), which was

much higher than the most efficient metal-free heterogeneous catalysts at the same

conditions.

Fig. 2.12 Effect of pressure. Reaction conditions: PO (14.3 mmol), catalyst (1.0mol%),

reaction time (1h), temperature (120oC).

0.5 1.0 1.5 2.0 2.5 3.0

20

30

40

50

60

70

80

90

Yield (%)

Selectivity (%)

Yie

ld a

nd s

ele

ctivity (

%)

Pressure (MPa)

47 | P a g e

Fig. 2.13 Effect of temperature Reaction conditions: PO (14.3 mmol), catalyst (1.0 mol%),

CO2 pressure (2.0 MPa), reaction time (1 h).

Fig. 2.14 Effect of reaction time Reaction conditions: PO (14.3 mmol), catalyst (1.0 mol%),

CO2 pressure (2.0 MPa), temperature (130oC).

100 110 120 130 140

40

50

60

70

80

90

100

Yield (%)

Selectivity (%)

Yie

ld a

nd

se

lectivity (

%)

Temperature (oC)

0 20 40 60 80

20

30

40

50

60

70

80

90

100

Yield (%)

Selectivity (%)

Yie

ld a

nd s

ele

ctivity (

%)

Time (h)

48 | P a g e

Fig. 2.15 Effect of catalyst amount. Reaction conditions: PO (14.3 mmol), CO2 pressure

(2.0 MPa), reaction time (20min), temperature (130oC).

Figure 2.16 Reuse of catalyst 3a. Reaction conditions: PO (14.3 mmol), catalyst (1.0

mol%), CO2 pressure (2.0 MPa), temperature (130oC), reaction time (20 min).

Recycling experiments showed that 3a could be reused four times with high

activity and selectivity (Figure 2.16). During the cycle experiments, the catalysts

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

30

40

50

60

70

80

90

Yield (%)

Selectivity (%)

Yie

ld a

nd s

ele

ctivity (

%)

Weight (mol%)

1 2 3 4

0

20

40

60

80

100

PC yied PC selectivity

Yie

ld a

nd s

ele

ctivity (

%)

Run Times

49 | P a g e

were easily recovered by simple filtration at room temperature, and then directly

used for the next cycle.

Figure 2.17 The TGA analysis of the catalysts (fresh and reused four times).

The thermogravimetric curve (Figure 2.17) showed no significate change after

4 times usage, which proved the high stability of the catalyst activity.

Figure 2.18 Reaction conditions: epoxides (14.3 mmol), catalyst (1.0 mol%), CO2

pressure (2.0 MPa), temperature (130oC), time (20min).

0 100 200 300 400 500

-0.2

0.0

0.2

0.4

0.6

0.8

1.0W

eig

ht

(%)

Temperature (oC)

UsedFresh

5a 5b 5c 5d 5e

0

20

40

60

80

100

120

6e6d6c6a

99%95%

85%86%

Substrates

O

OO

O PhO

OO

O

OO

Cl

O

OO

O

OO

C6H13

Yie

ld (

%)

92%

6b

50 | P a g e

Figure 2.19 Reaction conditions: PO (14.3 mmol), catalyst (1.0 mol %), CO2 pressure (0.1

MPa), and temperature (50 °C).

A battery of epoxide substrates was examined for the synthesis of

corresponding cyclic carbonates to test the adaptability of 3a to different epoxides.

As shown in Figure 2.18, 3a was suitable for a variety of terminal epoxides and

exhibited high yield of the corresponding cyclic carbonates. Among all the epoxides

surveyed, the activity of 5e was the highest, with 99 % yield of 6e achieved in 20

min.

To achieve the goal of finding an efficient catalyst that can react at mild

conditions, 3a catalysed cycloaddition of CO2 5c/5e were carried out under

atmospheric pressures of CO2 (0.1MPa) with a catalyst loading of 1 mol %, and the

reaction was run at 50°C. As shown in Figure 2.19, a 71% yield of 6c and 95% yield

of 6e could be obtained within 20 h at this CO2 pressure and temperature.

51 | P a g e

Scheme 2.2 Proposed mechanism for cyclic carbonates synthesis catalyzed by 3a.

Figure 2.20 Potential energy surface profiles of the 3a-catalyzed process and the

optimized geometries for the intermediates and transition states. See the APPENDICES

for computational details.

52 | P a g e

According to the reports and results above, a possible mechanism for fixation

of CO2 with epoxides was illustrated in Scheme 2.2, and we chose 3a as a

representative to study the mechanism details through DFT study (Figure 2.20). As

shown in Scheme 2.2 and Figure 2.20, firstly, 3a and PO interacted to form a

complex A, and then epoxy ring-opening step made A convert into intermediate B

via transition state TS1 with a barrier of 14.0 kcal/mol. A new complex C was formed,

when CO2 was added into the reaction system. Then, nucleophilic attack of the

intermediate on the complex C produced the alkyl carbonate D through TS2 with a

lower energy barrier of 2.9 kcal/mol. Finally, the cyclic carbonate was obtained by

intramolecular ring-closure and the catalyst was regenerated (TS3). The ring-

closure step was the rate limiting step with the highest energy barrier of 21.4

kcal/mol (TS3). The difference between ring-closure and ring-opening step was 7.4

kcal/mol. This could be attributed to the hydrogen bond-assisted ring-opening of

epoxide, which made the ring-opening much easier. Besides, there was some

negative effect of hydrogen bonding on the ring-closing event.

2.5 Conclusions

In summary, a series of carboxylic acid–based functional ionic liquids (CABFILs)

were facilely prepared by one-step synthesis method. They displayed reversible

temperature-controlled phase transitions in PC, which was much useful for the

coupling reaction and separation processes. CABFILs were successfully used in

reaction-separation for conversion of CO2 to carbonates under metal- and solvent-

free conditions. Besides, the IL 3a displayed high activity, and nearly 92% PC yield

was obtained within 20 min and could be readily separated by filtration at room

temperature for easy recycle. More importantly, 3a was suitable for a variety of

terminal epoxides. This approach helps to avoid further waste of the subsequent

separation step, as well as a highly effective way to combine the benefits of

heterogeneous and homogenous catalysts, which is of great interest from the

viewpoint of energy saving and chemical engineering.

53 | P a g e

Chapter 3: Efficient Transformation of CO2 to Cyclic

Carbonates by Bifunctional Protic Ionic Liquids under

Mild Conditions

3.1 Introduction

Carbon dioxide is one of the main components of flue gas, which is responsible

for the global warming. CO2 is also regarded as an abundant, nontoxic and

renewable C1 resource. [20–23] The utilization of CO2 as raw materials for

production of energy carriers and chemicals is a promising alternative, which can

reduce greenhouse gas thus alleviate the impact of climate change, whilst producing

various organic chemical commodities.[24–26,206–208] However, applications

related to CO2 are limited because of its thermodynamic stability and therefore the

CO2 activation always requires electrolytic reduction processes or high-energy input.

[27] One of the typical feasible routes is the synthesis of five-membered cyclic

carbonates by cycloaddition of CO2 with epoxides. As one of a few successfully

industrial products that efficiently utilize CO2 as a carbon feedstock, cyclic carbonate

can be wildly used as solvents in chemical processes,[33–35] electrolyte

components in lithium batteries,[36] useful monomers for acyclic carbamates[37,38]

and carbonates,[39] and intermediates in the production of fine chemicals, etc.

[40,41]

To date, various catalysts have been developed for the synthesis of useful

cyclic carbonates from CO2 and epoxides, such as metal-based catalysts, [24–

34]organocatalysts,[76,93,123,214–220] and ionic liquids etc.

[12,117,145,171,172,221–224]Although most of the catalyst systems show a good

yield to produce carbonates, high temperatures (>100 °C) and/or high CO2

pressures are always needed in these studies. Hence, great efforts have been

focused on the development of efficient and sustainable catalyst systems that can

be carried out chemically converting CO2 at relatively mild reaction conditions. In

this respect, many catalysts have been synthesized and exhibited a good

performance in the synthesis of cyclic carbonates from CO2. Metal−based catalysts

including metal-organic framework (MOF),[70,151] metal (salen) complex[225,226]

54 | P a g e

and metal-porphyrins[152–154] were reported to have a good yield of cyclic

carbonates at atmospheric pressure and/or room temperature for the activity sites

of metal ions and halide ions. For example, North and co-workers reported an Cr(III)

salphen complexes for the cycloaddition reaction under ambient conditions with the

presence of TBAB (tetrabutylammonium bromide).[147] The catalyst could catalyze

CO2 and epoxides to cyclic carbonates in 57−92% isolated yields after a reaction

time of 24 hours. Organocatalyst systems, such as boronic acids,[96]

tetraarylphosphonium salts (TAPS)[227] and pyridine-methanol/onium salts,[155]

could promote the cycloaddition of CO2 with epoxides under a moderate condition

due to the activation of epoxides by hydrogen bond (H-bond). Ionic liquids with a

strong hydrogen bond donor (HBD) were widely reported for this reaction. Aitor and

Israel et al[158] reported an imidazolium based iron-containing ionic liquid, and it

showed quantitative conversion and 94% chemoselectivity for the cycloaddition of

CO2 to epoxides under near ambient conditions. Park et al[160] developed a

pyridinium ILs-decorated MOF and used as solvent-free catalyst for CO2-oxirane

coupling reactions. The best catalyst displayed a high catalytic activity under 60 oC

and 1.2 MPa CO2 because of the synergetic effect of the IL functional sites. In

addition, we also demonstrated carboxylic acid-based ionic liquids that could

promote the cycloaddition reaction of CO2 at 50oC and 0.1MPa.[12] Recently studies

have been focused on protic ionic liquids, which exhibited not only excellent ability

of reversible CO2 capture but also highly efficient CO2 chemical conversion even

under ambient conditions because of the powerful H-bonding.[166–168] For

example, Han et al [169] employed a novel dual-ionic liquid system for cycloaddition

of epoxides with CO2 under temperature from 30 to 60 °C at 1 atm, the results

showed excellent yields without any solvents. However, compared to high

temperature and pressure catalysts, unsatisfactory activities and long reaction time

(>20h), presence of metals and/or toxic solvents are still drawbacks that need to be

overcome. It is a great challenge that designing efficient, green and metal-free

catalysts toward effective CO2 conversion under mild conditions.

55 | P a g e

Figure 3.1 ILs used in this study.

Inspired by these works, we reported here the synthesis of DBU-based

bifuncitional protic ionic liquids (DBPILs) by acid-base reaction at room temperature

based on good acidity of halogenated carboxylic acid and alcohols that caused by

inductive effect of the electron-withdrawing group (Figure 3.1). DBPILs that

composed by alkoxy anion, protic acid and nucleophilic groups were successfully

used in cycloaddition reaction of CO2 with epoxides at 1 bar CO2 and 30/50 oC. We

found that they were efficient metal-free catalysts for this reaction, which displayed

high activity in producing carbonates without the need for long reaction time or co-

catalyst. And we explored the influence of the substrate scope on the catalytic

behaviour with various epoxides and simulated flue gas. DFT studies, IR spectrum

and experiments were conducted to study mechanism of the activation of CO2 and

H-bond interaction between DBPILs and epoxide.


Carbon dioxide and nitrogen were supplied by Beijing Analytical Instrument

Factory with a purity of 99.99% and 99.999% separately. Simulated flue gas was

made by controlling the gas flow rate (CO2:N2=3:17) using gas flowmeter. 1,8-

diazabicyclo-[5.4.0]undec-7-ene (DBU 99%), 4-dimethylaminopyridine (99%),

bromoethane (98%), bromoacetic acid (98%), 2-bromoethanol (95%), 1,3-dibromo-

2-propanol (95%), 4-bromophbenol (98%), 1-butyl-3-methylimidazolium bromide

(97%) and all of the epoxides unless otherwise specified were bought from Aladdin

56 | P a g e

Reagent Co. Glycidyl phenyl ether was bought from TCI Shanghai. Lithium

Bis(trifluoromethanesulphonyl)imide and ethylacetate were bought from Sinopharm

Chemical Reagent Co., Ltd, and were used without further purification. All

calculations were carried out with B3LYP-D3/6-31+G** level implemented in

Gaussian 09 package. The Cartesian coordinates can be found in APPENDICES.



To synthesize the protic ionic liquids, electron withdrawing groups are selected

to increase acidity of alcohols and carboxylic acid through inductive effect. Halogens

are well known as electron-withdrawing groups. It has been proven that Br- is an

excellent nucleophilic ion for the cycloaddition reaction in our previous

work.[145,223] Herein, halogenated carboxylic acid and alcohols with a short chain

length (the closer of the halides and acid, the stronger inductive effect) are chosen

to react with super base DBU. During the experiments, a series of DBPILs

composed by protonic acid and nucleophilic groups was prepared by acid-base

neutralizing reaction at room temperature. DBU based ionic liquid with a phenolic

hydroxyl group (1d) was prepared by DBU and 4-bromophbenol due to the weak

acidity of 4-bromophbenol attributed to the conjugative effect and the long chain

length between bromide and hydrogen group (Details are shown in supporting

information Scheme 3.1). 4-dimethylaminopyridine (DMAP) based ILs (1e) were

synthesized according to the literature[228] (Scheme 3.2). DBU-based catalysts 1g

with NTF2 was synthesized with ion-exchange method (Scheme 3.3).


All of the DBU-based catalysts with bromide were synthesized by using one-

step method. 1b was chosen as a model to show the process. In a typical reaction,

bromoacetic acid (20.00 mmol) was dissolved in ethyl acetate. Then DBU (40.00

57 | P a g e

mmol) was dropped into the flask. The mixture was stirred for an hour at room

temperature. After the reaction, the top phase was immediately poured out and the

residue liquid was washed three times with ethyl acetate in separatory funnel and

dried at 50oC for 24 h under vacuum. Finally, a viscous liquid was obtained.

Scheme 3.2 One step synthesis of catalyst 1e.

4-dimethylaminopyridine (DMAP) based ILs (1e) were synthesized according

to the literature[228]. In a typical reaction, DMAP (50.00 mmol) and 2-bromoethanol

(60.00 mmol) were dissolved in ethyl acetate and added into a 250 mL three-necked

flask. The mixture was stirred for 12 h at 50 oC. When it is cool down, the top phase

was poured out and the solid was washed three times with ethyl acetate and dried

at 50oC in a vacuum oven for one day.

Scheme 3.3 Synthesis of catalyst 1g in this study.

DBU-based catalysts 1g with NTF2 was synthesized by using ion-

exchange method. In a typical reaction, 1f (4.00 mmol) was added into a 250 mL

flask and dissolved in water. Then Lithium Bis(trifluoromethanesulphonyl)imide

(10.00 mmol) was poured into the flask. The mixture was stirred for 24 h at room

temperature. After the reaction, the top phase was poured out and the residue was

washed n three times with water in separatory funnel. Then the product was dried

at 50oC for 24 h under vacuum.

58 | P a g e


The morphology was observed through a scanning electron microscope (JEOL

JSM 6700F). Fourier transform infrared (FT-IR) spectra were recorded on a Thermo

Nicolet 380 spectrophotometer with anhydrous KBr as standard (Thermo Electron

Co.). NMR spectra were recorded on a Bruker AVANCE III HD 600 spectrometer

with DMSO-d6 as solvent.

3.3.3 Procedure of the cycloaddition reaction of CO2 with epoxide

Figure 3.2 Photographic image shows the process of the reaction


Schlenk tube with a magnetic stirrer and an automatic temperature control system.

In a typical reaction, 0.5ml of epichlorohydrin and appropriate amounts of catalyst

were charged into the reactor at room temperature. Then, a balloon of CO2 was

connected to the schlenk tube, control the temperature within the desired range

afterwards. After the reaction, the remaining CO2 was vented out slowly. The yield

of the products was characterized by HNMR spectroscopy of the crude reaction

mixture by using CDCl3 as solvents.

3.3.4 Recycle experiment

After the reaction, 10 ml water was poured in to the schlenk tube to wash the

product. The mixture was stirred for 1 h at room temperature. The product was

59 | P a g e

separated from the mixture by filtration and washed one more time with water.

Afterwards, the product was dried at 80 oC for 24 h under vacuum. The yield of the

product was calculated by weight. The liquid phase was first separated with 2f in a

separatory funnel. Then water was removed by vacuum distillation. The obtained

catalysts were washed three times by ethyl acetate and dried at 50oC for 24 h under

vacuum, and ready for the recycling experiment.

3.3.5 Characterization of the catalysts and cyclic carbonates

Characterization of the catalysts

DBU:

Liquid:1H NMR (600 MHz, DMSO): 3.14 (dd, J = 10.8, 3.7 Hz, 4H), 3.09 – 3.04

(m, 2H), 2.27 – 2.21 (m, 2H), 1.64 (dq, J = 8.1, 5.9 Hz, 2H), 1.57 (ddd, J = 11.0, 5.6,

2.0 Hz, 2H), 1.54 – 1.45 (m, 4H). 13CNMR (151 MHz, DMSO): 159.50, 51.75, 47.44,

43.45, 36.33, 29.02, 28.06, 25.74, 22.31.

1a:

Solid powder:11H NMR (600 MHz, DMSO): δ 3.68 – 3.62 (m, 2H), 3.57 (q, J =

7.2 Hz, 2H), 3.48 (dt, J = 17.0, 5.8 Hz, 4H), 2.92 – 2.86 (m, 2H), 2.04 – 1.90 (m, 2H),

1.74 – 1.67 (m, 2H), 1.67 – 1.58 (m, 4H), 1.16 (t, J = 7.2 Hz, 3H). 13C NMR (151

MHz, DMSO):165.67, 53.86, 48.41, 48.08, 45.87, 27.69, 27.00, 25.46, 22.65, 19.61,

13.58.

1b:

Viscous solid: 1H NMR (600 MHz, DMSO): δ 9.69 (s, 1H), 3.55 (dd, J = 19.5,

15.0 Hz, 4H), 3.49 (t, J = 5.8 Hz, 4H), 3.30 (d, J = 31.3 Hz, 2H), 3.25 (t, J = 5.7 Hz,

4H), 2.80 – 2.57 (m, 4H), 2.02 – 1.85 (m, 4H), 1.72 – 1.65 (m, 4H), 1.65 – 1.57 (m,

8H). 13C NMR (151 MHz, DMSO): 165.37, 53.36, 47.87, 37.52, 31.59, 28.19, 25.89,

23.28, 18.84.

1c:

Slid: 1H NMR (600 MHz, DMSO): δ 9.67 (s, 1H), 3.60 – 3.54 (m, 4H), 3.50 (t, J

60 | P a g e

= 5.8 Hz, 4H), 3.33 (s, 2H), 3.26 (t, J = 5.7 Hz, 4H), 2.78 – 2.62 (m,4H), 1.96 – 1.87

(m,4H), 1.72 – 1.65 (m, 4H), 1.65 – 1.57 (m, 8H). 13C NMR (151 MHz, DMSO):

165.35, 53.63, 48.18, 37.48, 31.52, 27.89, 25.66, 23.29, 19.13.

1d:

Slid: 1H NMR (600 MHz, DMSO): δ 12.04 (s, 1H), 7.30 – 6.89 (m, 2H), 6.61 –

6.45 (m, 2H), 3.34 (dd, J = 11.4, 6.9 Hz, 2H), 3.31 (t, J = 5.9 Hz, 4H)., 3.16 (t, J =

5.6 Hz, 2H), 1.83 – 1.75 (m, 2H), 1.65 – 1.57 (m, 2H), 1.57 – 1.49 (m, 4H). 13C NMR

(151 MHz, DMSO): δ 163.52, 162.08, 131.48, 118.69, 105.41, 52.63, 47.65, 32.87,

28.56, 26.77, 24.33, 20.22.

1e:

Slid: 1H NMR (600 MHz, DMSO) δ 8.35 (t, J = 5.4 Hz, 1H), 8.18 (dd, J = 5.7,

1.4 Hz, 1H), 7.15 – 6.95 (m, 1H), 6.80 (dd, J = 5.7, 1.5 Hz, 1H), 4.37 (t, J = 6.6 Hz,

1H), 3.30 (s, 1H), 3.19 (s, 3H), 3.08 (s, 2H), 2.83 (t, J = 6.6 Hz, 1H). 13C NMR (151

MHz, DMSO): 172.00, 155.82, 155.49, 143.85, 142.34, 107.40, 106.80, 52.89,

35.26.

1f:

Slid: 1H NMR (600 MHz, DMSO): δ 9.61 (s, 1H), 3.64 – 3.53 (m, 6H), 3.49 (t, J

= 5.8 Hz, 6H), 3.30 (s, 4H), 3.26 (t, J = 5.7 Hz, 6H), 2.75 – 2.65 (m, 6H), 2.09 (s,

1H), 1.96 – 1.86 (m, 6H), 1.73 – 1.65 (m, 6H), 1.65 – 1.54 (m, 12H). 13C NMR (151

MHz, DMSO): 165.39, 53.38, 47.89, 37.53, 31.60, 28.19, 25.89, 23.29, 18.85.

1g:

Liquid: 1H NMR (600 MHz, DMSO): δ 9.61 (s, 1H), 3.64 – 3.53 (m, 6H), 3.49 (t,

61 | P a g e

J = 5.8 Hz, 6H), 3.30 (s, 4H), 3.26 (t, J = 5.7 Hz, 6H), 2.75 – 2.65 (m, 6H), 2.09 (s,

1H), 1.96 – 1.86 (m, 6H), 1.73 – 1.65 (m, 6H), 1.65 – 1.54 (m, 12H). 13C NMR (151

MHz, DMSO): 165.39, 53.38, 47.89, 37.53, 31.60, 28.19, 25.89, 23.29, 18.85.

Spectra of product 1H NMR and 13C NMR of Products:

4-chloromethyl-1, 3-dioxolan-2-one:

1H NMR ((CDCl3, TMS, 400 MHz): 3.84 (d, J = 6.0 Hz, 2H), 4.05 (t, J = 8.4 Hz,

1H), 4.60 (t, J = 8.0 Hz, 1H), 5.07–5.10 (m, 1H). 13C NMR (CDCl3, TMS, 100 MHz):

44.15, 70.46, 73.51, 154.94.

3a:

1H NMR ((CDCl3, TMS, 400 MHz): 3.84 (d, J = 6.0 Hz, 2H), 4.05 (t, J = 8.4 Hz,

1H), 4.60 (t, J = 8.0 Hz, 1H), 5.07–5.10 (m, 1H). 13C NMR (CDCl3, TMS, 100 MHz):

44.15, 70.46, 73.51, 154.95.

3b:

1H NMR ((CDCl3, TMS, 400 MHz): 1.63 (s, 3H), 3.67 (d, J = 11.57 Hz, 1H), 3.75

(d, J = 12.1 Hz, 1H), 4.21 (d, J = 8.8 Hz, 1H), 4.53 (d, J = 8.8 Hz, 1H). 13C NMR

(CDCl3, TMS, 100 MHz): 44.15, 70.46, 73.51, 154.95.

3c:

1H NMR (CDCl3, TMS, 400 MHz): 3.63 (dd, J = 4.0, 11.2 Hz, 1H), 3.70 (dd, J =

4.0, 11.2 Hz, 1H), 4.02–4.11 (m, 2H), 4.41 (dd, J = 6.4, 8.0 Hz, 1H), 4.51 (dd, J =

8.4, 8.4 Hz, 1H), 4.79–4.85 (m, 1H), 5.22–5.32 (m, 2H), 5.83–5.93 (m, 1H); 13C NMR

(100 MHz, CDCl3) δ 65.9, 68.6, 72.0, 75.0, 117.1, 133.5, 154.8.

3d:

1H NMR (CDCl3, TMS, 400 MHz): 4.34 (t, 1H, J = 8.4 Hz); 4.80 (t, 1H, J = 8.4

Hz); 5.68 (t, 1H, J = 8.0 Hz); 7.35–7.44 (m, 5H); 13C NMR (CDCl3, TMS, 100 MHz):

71.10, 77.92, 125.81, 129.12, 129.63, 135.70, 154.81

62 | P a g e

3e:

1H NMR (CDCl3, TMS, 400 MHz): 0.88 (t, J = 7.5 Hz, 1H), 1.32 (dq, J = 14.8,

7.4 Hz, 2H), 1.42 – 1.56 (m, 2H), 3.46 (t, J = 6.5 Hz, 2H), 3.56 (dd, J = 11.5, 4.2 Hz,

1H), 3.63 (dd, J = 11.5, 2.7 Hz, 1H), 4.25 (dd, J = 8.3, 5.9 Hz, 1H) 4.52 (t, 3J = 8.4

Hz, 1H), 4.91 (dddd, J = 8.6, 6.0, 4.1, 2.8 Hz, 1H), 13C NMR (CDCl3, TMS, 100 MHz):

13.55, 18.63, 31.06, 66.00, 69.52, 70.54, 75.48, 154.88.

3f:

1H NMR (CDCl3, TMS, 400 MHz): 4.15 (dd, 3J = 4.4 Hz, 2J = 10.8 Hz, 1H), 4.24

[dd, 3J = 3.6 Hz, 2J = 10.8 Hz, 1H), 4.55 (dd, 3J = 8.4 Hz, 2J = 6 Hz, 1H), 4.62 (t,

3J = 8.4 Hz, 1H), 5.03 (m, 1H), 6.91 [d, 3J = 8.0 Hz, 2H), 7.08 (s, 1H), 7.31 (t, 3J =

8.0 Hz, 2H). 13C NMR (CDCl3, TMS, 100 MHz): 66.17, 68.84, 74.11, 114.57, 121.92,

129.62, 154.65

3g:

1H NMR (CDCl3, TMS, 400 MHz): 2.13 (s, 3H), 4.18 (dd, J = 11.2, 3.5 Hz, 1H),

4.27 (dd, J = 11.2, 2.4 Hz, 1H), 4.47 (dd, 3J = 8.4 Hz, 5.2Hz, 1H), 4.64 (t, 3J = 8.5

Hz, 1H), 5.17 (m, 1H), 6.88 (td, J = 7.4, 0.8 Hz, 1H), 6.93 (d, J = 7.8 Hz, 1H), 7.14-

7.17 (m, 2H). 13C NMR (CDCl3, TMS, 100 MHz): 15.49, 66.17, 68.84, 74.11, 114.57,

121.92, 129.62, 154.65

3h:

1H NMR (CDCl3, TMS, 400 MHz): 1.52 – 1.55 (m, 2H), 3.46 (t, J = 5.9 Hz, 2H),

3.55 (dd, J = 11.5, 4.2 Hz, 1H), 3.63 (dd, J = 11.5, 2.7 Hz, 1H), 4.25 (dd, J = 8.2 5.9

Hz, 1H) 4.52 (t, 3J = 8.4 Hz, 1H), 4.91 (dddd, J = 8.6, 5.9, 4.2, 2.8 Hz, 1H), 13C NMR

(CDCl3, TMS, 100 MHz): 25.60, 66.09, 69.51, 70.55, 75.50, 154.93.

63 | P a g e


3.4.1 Activities of various catalysts

The catalytic activities of various DBPILs were carried out with epichlorohydrin

and 1 bar of CO2 (balloon) in a schlenk tube at 30 °C. The results were shown in

Table 3.1. It was found that the common ILs [bmim]Br (Table 3.1, entry 1) had a low

activity in catalysing the reaction. Interestingly, DBU-based ILs without protonic acid

(1a) was observed a similar activity with [bmim]Br (Table 3.1, entry 2 vs 1), which

indicated that cation may have little effects on the reaction. Then the activity of DBU-

based ILs composed by protic acid and bromine ion (1b and 1c) was studied at the

same conditions, and showing a very high yield of chloropropene carbonate (CPC)

(70% and 76% respectively) as compared to 1a that without protic acid (Table 3.1,

entry 3, 4 vs 2). The possible reason maybe that the protic acid of DBPILs could

activate epichlorohydrin efficiently by the powerful H-bond interaction. Besides, as

a nucleophilic anion, alkoxy anion might play the same role with Br-, which could

increase the active site.

Table 3.1: Reactions of CO2 with epichlorohydrin catalyzed by different ILsa

Entry Catalyst Time (h) Yieldb (%)

1c [Bmim]Br 6 23

2 1a 6 26

3 1b 6 70

4 1c 6 76

5 1d 6 14

6 1e 6 47

7 1f 6 92

8 1g 10 4

9d 1f 10 91

aReaction conditions: epichlorohydrin (0.5ml), ILs (6 mol%), 1 bar of CO2 (balloon),

Temperature (30oC). bDetermined by 1H NMR. cCatalstys (8 mol%), d Catalyst ( 4 mol %),

Temperature (25oC).

To compare the effect of H-bond interaction, DBU based ionic liquid with a

64 | P a g e

phenolic hydroxyl group (1d) was prepared by DBU and 4-bromophbenol. Even

phenolic hydroxyl group was reported a good HBD[229,230], but in this study, 1d

only showed a low activity of 14%. 4-dimethylaminopyridine (DMAP) based ILs (1e)

with a hydroxyl group, which had been reported as an efficient catalyst for this

reaction in our previous work,[12] was also investigated (Table 3.1, entry 6). 1e

showed a promising yield of CPC (47%) for the hydroxyl group activating

epichlorohydrin (Table 3.1, entry 6 vs 1, 2), but much lower than DBU based protic

ionic liquids (DBPILs). The possible mechanism was speculated that hydrogen

proton from DBPILs had a stronger H-bond interaction with epoxide than –OH group

from 1e, which made the ring open of epoxide much easier, and resulted in the

higher activity of DBPILs compared to 1e (Table 3.1, entries 3, 4 vs 6). Then, DBPILs

1f incorporated with protonic acid and multi-nucleophilic sites was prepared and

used for this reaction. It showed the highest CPC yields of all the catalysts at the

same conditions with aforementioned studies (Table 3.1, entry 7). To find whether

alkoxy anion can play the same role with bromine ion, DBPILs 1g without bromine

ion was prepared and used in this reaction. Only 4% yield of CPC was obtained

after 10 hours as shown in Table 1 (Entry 8), which demonstrated that the alkoxy

anion had little effect on catalytic performance of this reaction. Surprisingly, 1f

showed a 91% yield of CPC within 10 hours at room temperature (Table 3.1, entry

9), while the reported pincer-type compounds catalysts,[231] which had the highest

TON and/or TOF for organocatalysts under ambient conditions, took 24 hours to

reach 92% yield of CPC. In view of this, 1f was chosen as benchmark catalyst to

investigate influence of reaction parameters.

3.4.2 Effect of reaction conditions

The effects of reaction time and temperatures were presented in Figure 3.3.

The yields of CPC increased rapidly to 82% within the first 4 h at 30 oC, and then

slowly reached to 96% in the next 4 hours. The results indicated an obviously

decrease of reaction rates. As the reaction temperature increased to 50 oC, the yield

of CPC increased to 98% sharply in 4 h without an obvious slow-growth stage. This

may be caused by the increasing viscosity of the reaction system with the producing

of CPC, which have a negative effect on the CO2 transferring in the liquid phase.

The mechanism mentioned above was confirmed by the same behaviour of the

65 | P a g e

catalyst loading study shown in Figure 3.4, which also had a slow-growth stage with

the increasing of 1f.

Figure 3.3 Effects of reaction time and temperature catalyzed by 1f. Reaction conditions:

epichlorohydrin (0.5ml), ILs (6 mol%), CO2 (balloon).

Figure 3.4 Effects of catalyst amount catalyzed by 1f. Reaction conditions:

epichlorohydrin (0.5ml), CO2 (balloon), temperature (30 oC), time (8 h).

0 2 4 6 80

20

40

60

80

100

Time (h)

30 oC

50 oC

Yie

ld (

%)

0 2 4 6 840

60

80

100

Yie

ld (

%)

Amount (%)

66 | P a g e

3.4.3 Catalytic activity of epoxides with simulated flue gas and

SO2

Figure 3.5 Cycloaddition of epichlorohydrin with simulated flue gas (a) and SO2 (b)

catalysed by 1f, and photographic image show the phase change of 1f after the

absorption of SO2 (c).

CO2 is known as the main component of dry flue gas. More attentions has been

paid on the conversion of CO2 from the flue gas.[20,150,212] In order to investigate

whether DBPILs could be used in the flue gas, a 15% CO2/85% N2 system was

chosen to simulate flue gas for the cycloaddition reaction with epoxides (Figure 3.5).

However, only 24% of CPC was obtained within 6 hours catalysed by 1f, which was

much lower than pure CO2 at the same conditions (24% vs 92%). The yield of CPC

can reach to 91% after 36 hours reaction. The results indicated the feasibility for

conversion of CO2 in the flue gas catalysed by DBPILs, but the comparably low

activity was still the drawback need to be overcome. Then we change the flue gas

to SO2 (another component of flue gas), catalyst 1f exhibited extremely high activity

(Figure 2.5 b), a 96% of 4f could be obtained within half an hour at room temperature.

The most important reason was that SO2 was much more activity than CO2.

Furthermore, when we did the experiments, we found that 1f would transfer from

solid to liquid after the absorption of SO2 (See Figure 2.5 c). Then, the SO2

absorptivity of 1f was investigated by experiment. The results showed that 1f could

show a high SO2 capacity of 1.1g SO2 per gram 1f (12 mol SO2/1f).

67 | P a g e

3.4.4 Catalytic activity to various epoxides

Table 3.2: Reaction of CO2 with substrates catalysed by 1fa

30oC, 6%, 6h, 3a: 88% 3%, 6h, 3b: 65% 3%, 6h, 3c: 94%

6%, 6h, 3d: 87% 2%, 12h, 3e: 89% 6%, 6h, 3f: 97%a,

95%b

3%, 8h, 3g: 97% 3%, 8h, 3h: 84%

aYields were determined by NMR. bIsolated yields were determined by weighting.

A range of different substituted terminal epoxides were examined under a

balloon of CO2 condition in the presence of 1f DBPILs. The results were summarized

in Table 3.2. Epibromohydrin (2a) could afford the product 3a in a good yield of 88%

at the optimal condition. Taking into account of the industrial application, the loading

of 1f was reduced, and the reaction temperature increased to 50oC. However, the

carbonate 3b showed much lower yield than 3c at the same condition, which

probably due to the high stereo-hindrance effect. Furthermore, styrene oxide 2d and

glycidol derivatived 2e-2h were examined. All of these epoxides generated the

corresponding cyclic carbonates in good yields (3d-3h).

68 | P a g e

3.4.5 Recycling of the catalyst

Figure 3.6 Recycle experiments catalyzed by 1f. a Reaction conditions: 2f (0.5 ml), 1f (6

mol%), 1bar CO2 (balloon), Temperature (50 oC), Reaction time (6 h).

2f was subsequently chosen as an optimal terminal epoxide to study the

cycling performance of DBPILs 1f. When we tried to recycle 1f after the reaction,

we found that the yield of 3f decreased obviously from 95% to 77% after four runs

(Figure 3.6). Based on the report, the reduction of catalytic activity after used might

be caused by the partial loss of the catalyst for the sublimation property[166] or

catalyst addition to epoxides[158,227]. Then, a series of experiments were designed

to study the reason of the decreased activity. The experiments and spectrum results

indicated that the DBPILs 1f could addition to 2f and further generate 1h with a

hydroxyl group, because of the “super-dissociating” feature of the protic ionic

liquids.[232] Furthermore, 1h could not activate CO2 and had a relatively weak H-

bond interaction with epoxide compare to the powerful H-bonding of 1f, which led to

the reduction of the yields in the recycle experiments.

1 2 3 4

0

20

40

60

80

100

Yie

ld (

%)

Run times

69 | P a g e

Scheme 3.4. Mechanistic studies by experiments

A series of experiments were designed to study the reason of the low activity

(Scheme 3.4). The results indicated that the DBUPILs 1f would react with 2f to

produce 1h with a hydroxy group (Scheme 3.4 A). The structure of 1h was

demonstrated by NMR spectrum (Figure 3.7).

Figure 3.7 HNMR of 1f and 1h.

70 | P a g e

However, DBU based ILs 1a without a protonic acid could not react with 2f

(Scheme 3.4 B). The above results suggested that 1f could react with epoxide 2f to

generate 1h and DBU, leading to the unrecyclable of catalyst 1f and a low activity

of the catalyst system. The hydrogen proton and alkoxy anion might play key roles

in the reaction of DBUILs and epoxide. Subsequently, a probable mechanism of 1e

reacted with epoxide 2f was proposed. The detail was shown in the supporting

information (Scheme 3.5). First, the strong H-bond between DBUPILs and epoxide

led to the ring-open step (step 1), then the proton transfer (step 2) finally resulted in

the formation of 1g and DBU (step 3). These results also suggested that DBUPILs

were excellent epoxy ring-open catalysts at mild conditions, which could be widely

used in the other ring-open reaction of epoxide.

Scheme 3.5 probable mechanism of 1e reacted with epoxide 2f

In order to identify whether 1h was a reactive intermediate of the catalytic cycle.

First, 1h was submitted to the CO2 fixation conditions without epoxide, and no

carbonate 3f was obtained at all (Scheme 3.4 C). Next, we found 1h could catalytic

epoxide 2f to afford the corresponding carbonate 3f (Scheme 3.4 D), and 1h was

not changed at the end of the reaction. However, the yield of 3f catalyzed by 1h was

only 74%. By contrast, 1f exhibited an excellent yield of 3f (95%, Table 2) at the

same condition. The probable reason maybe that the H-bond interaction between –

OH group and epoxide was weaker than hydrogen proton. Then, the catalytic activity

of 1h mixed with DBU was studied to compare with 1f and 1h at the same condition,

because 1h and DBU were ring-open species during the cycloaddition reaction

catalyzed by 1f (Scheme 3.4 A). As compared to 1h, the 1h/DBU system had a 88%

yield of carbonate (Scheme 3.4 E), which was much higher than 1h (74%). This

might be caused by the absorption and activity of CO2 by DBU. But 1h/DBU system

71 | P a g e

had a lower activity than 1f (95%). The possible reason maybe that the hydrogen

proton from 1f could have a stronger H-bond interaction with epoxide than –OH

group from 1g, whilst alkoxy anion of 1f played the same role with DBU.

3.4.6 Studies of reaction mechanism

Figure 3.8 FT-IR spectra of the activation of CO2

FT-IR spectra were employed to identify whether alkoxy anion of 1f could

activate CO2. As shown in Figure 3.8, a new band at 1795 cm-1 appeared after the

reaction of CO2 with 1f, which corresponded to the new asymmetric (C=O) vibration

of the carbamate salt, thus implying the activation of CO2 by 1f.

3500 3000 2500 2000 1500 1000 500

In

ten

sit

y

Wavenumber (cm-1)

1f

1f+CO2

72 | P a g e

Figure 3.9 Comparisons of the relative energy of the ring-open step.

It is reported that H-bond interaction between catalyst and epoxide can reduce

the activation energy of ring-open step.[223] Hence, comparison of 1f and 1h

catalyzed ring-open step was examined by DFT study to identify whether hydrogen

proton from 1f had a more powerful H-bond interaction with epoxide than –OH group

from 1h. All calculations were carried out with B3LYP-D3/6-31+G** level

implemented in Gaussian 09 package. As shown in Figure 3.9, 1h-catalyzed ring-

open step has an energy barrier of 44.2 kcal/mol, which is a little higher than 1f-

catalyzed process (39.6 kcal/mol). The hydrogen atom of 1h is coordinated with the

oxygen of epoxide through a hydrogen bond leading to the length of the C–O bond

increased from 1.455 Å to 2.099 Å, which makes the ring-opening much easier. The

same interaction can be found from 1f and epoxide. The length of hydrogen protons

of 1f and oxygen of epoxide is closer than 1h (1.502 Å), the increased length of the

C–O bond caused by hydrogen bond of 1f and epoxide is a little longer (from 1.455

Å to 2.102 Å) than 1h. The results indicated a higher activity of 1f than 1h due to

the stronger H-bond interaction, which was well consistent with our experiment

results.

73 | P a g e

3.4.7 Probable mechanism for fixation of CO2 with epoxide

Figure 3.10 Potential energy surface profiles of 1f-catalyzed process and the optimized

geometries for the intermediates and transition states.

Based on all the results above, a possible mechanism of the 1f-catalyzed

process is proposed, and the DFT study was used to study the mechanism. As

shown in Scheme 3.6 and Figure 3.10, the H-bond interaction between 1f and

epoxide firstly made the length of C-O bond increased, which could improve the

ring-open process of epoxide (step 1). The attack of bromide ion to epoxide resulted

in the ring-open of epoxide and made A convert into intermediate B (step 2) via

transition state TS1 with a barrier of 39.6 kcal/mol. As CO2 was added into the

-30

-20

-10

0

10

20

30

40

En

erg

y(k

ca

l/m

ol)

0.0

A

TS1

BC

TS2

D

TS3

E

39.6

-5.3-8.4

2.9

-6.3

7.9

-23.6

74 | P a g e

reaction system, it could be activated by alkoxy anion, and led to the formation of

complex C (step 3). Subsequently, the alkyl carbonate D generated by the

nucleophilic attack of the intermediate through TS2 through a low energy barrier of

2.9 kcal/mol (step 4). Finally, the cyclic carbonate was obtained by ring-closure step

with an energy barrier of 7.9 kcal/mol (TS3). The study illustrated that the epoxy

ring-open step was a rate–limited step with the highest energy barrier of 39.6

kcal/mol (TS1).

Scheme 3.6. Mechanism of the cycloaddition reaction catalysed by 1f.

3.5 Conclusions

In summary, this work exhibits a simple way to prepare DBPILs by introducing

electron withdrawing groups to O-H acid. The DBPILs with protonic acid and

nucleophilic sites were used as single-component and metal-free catalysts in the

cycloaddition reaction of CO2 with epoxides at very mild temperature and 1 bar CO2

conditions. DBPILs showed a great improvement of catalytic activity and good

substrate compatibility to various epoxides. Furthermore, DBPILs were found

suitable for the conversion of simulated flue gas. The results from experiments,

spectrum and DFT illustrated the activation of CO2 of DBPILs and strong H-bond

75 | P a g e

interaction between DBPILs and epoxide. This study provides a high efficient epoxy

ring-open catalyst for transformation of CO2 with epoxide. The greatly improved

catalytic activity makes DBPILs a promising environmentally benign catalyst for the

applications of CO2 conversion at mild conditions.

76 | P a g e

Chapter 4: Aluminium-containing Ionic Liquid for

Cycloaddition of CO2 with Epoxides under Mild Conditions

4.1 Introduction

Carbon dioxide is considered as an abundant, easily available and renewable C1

building block.[20,23] As an efficient way for CO2 utilization, chemical conversion of CO2

has always been a hot question in not only academia but also international industry.[24–

26] However, CO2 conversion is limited because of its inherent thermodynamic stability,

thus resulting in low reactivity and high energy inputs. [27] Although CO2 is

thermodynamically stable, some progresses have been achieved in recent years[233].

One potentially useful strategy is the 100% atom-economical cycloaddition reaction of

CO2 and epoxides to five-membered cyclic carbonates (Scheme 4.1). [21,234,235]

Scheme 4.1 Synthesis of cyclic carbonates

In this context, the key issue to convert CO2 and epoxide into cyclic carbonates is

focused on the activation of CO2 and epoxides. Therefore, effective catalytic systems are

highly required. So far, many efficient catalysts have been developed for the cycloaddition

of CO2 and epoxides, such as metal containing complexes[71,74,75,85,147,209–213],

metal-organic framework (MOF),[70,151] metal (salen) complex[225,226] and metal-

porphyrins[152–154]), organocatalysts[76,93,96,123,155,214–220,227] and ionic

liquids.[12,117,145,158,160,171,172,221–224,236] However, high temperature and

pressure are generally needed. In recent years, researchers have paid much attention to

chemically convert CO2 with epoxides under mild reaction conditions, especially at

atmospheric pressure and room temperature. Though much progress has been made,

the chemical conversion of CO2 at atmospheric pressure and room temperature is still a

challenge. For example, the use of metal containing catalysts consisting of an

electrophilic metal ion and a nucleophilic halide ion will significantly accelerates the

process under mild conditions. [152,225,226] Andy Hor and Wu[225] reported a salen

based molecular cage complexed with Co and Al. These catalysts were found to be

efficient catalysts for the cycloaddition of CO2 with styrene oxide at 25 °C and 1 atm CO2.

77 | P a g e

Organocatalysts systems have also attracted increasing attentions to promote the

cycloaddition reaction of CO2 under a moderate condition because of the activation of

epoxides by a strong hydrogen bond donor, including boronic acids,[96] ascorbic acid[91]

and pyridine-methanol/onium salts [155] etc. Liu et al[231] reported series of pincer-type

compounds with a carboxyl group as proton transfer agent used to catalyze cycloaddition

of epoxides with CO2. These multifunctional catalysts were demonstrated the highest

TON and/or TOF for organocatalysts under room temperature and 1 bar of CO2. Ionic

liquids (ILs) have been widely reported in the cycloaddition reaction of CO2 under mild

conditions, because of the unique features such as high thermal and chemical stability,

easy recyclability, and turnable properties. Specifically, some ionic liquids with a strong

hydrogen bond donor (HBD) have displayed an excellent performance for this conversion

of CO2 to carbonates with epoxides under ambient conditions through carefully design of

activity sites and HBD.[158,165,168,236] For example, Han et al[169] prepared a novel

dual-ionic liquid system for cycloaddition of epoxide with CO2 under mild conditions (1

atm CO2, T = 30–60 °C), the results showed excellent yields without any solvents. Wang

et al [165] reported a dual hydroxyl functional mesoporous poly(ionic liquid)s as recyclable

heterogeneous catalysts for cyclic carbonate synthesis from CO2 and epoxides in the

presence of tetrabutylammonium iodide at 70 °C and 0.1/0.4 MPa. The catalyst could be

easily reused after stable activity.

Figure 4.1 Structure of catalyst used in this study

We have also found that by using DBU based bifunctional protic ionic liquids (DBPILs)

as metal and solvent-free catalysts, CO2 could react with epoxide at 30 oC and 1 bar CO2

and produce cyclic carbonates in excellent yields without the need for time-consuming

78 | P a g e

and co-catalyst because of the powerful hydrogen bond interaction (H-bonding) with

epoxides. However, the “super-dissociating” feature of the protic ionic liquids[232] made

the proton from DBPILs added to epoxide, and led to the reduction of the yields in recycle

experiments.

It is reported that electrophilic metal ion can significantly accelerate the process, and

aluminum has been illustrated a very powerful metal ion to activate epoxide[225]. Inspired

by this, a strategy was employed to solve the recycling of DBPILs by using aluminum ion

to replace proton from DBPILs. In this work, we designed a DBU based ionic liquids

containing aluminum (DILA) catalyst based on dissociating feature of proton from DBPILs

(Figure 4.1). DILA was successfully used to catalyze the cycloaddition reaction of CO2

with epoxides at 1 bar and room temperature. As a single component catalyst, this

DBPILs could show superior yield of carbonates with broad epoxide substrate scope

because the activate epoxides by the powerful aluminum ion and nucleophilic bromide

ion. Moreover, the DILA could be easily recovered and reused at least 4 times without

obviously activity loss.


4.2.1 General information

Carbon dioxide was supplied by Air Liquide Danmark with a purity of 99.995%. 1,8-

diazabicyclo-[5.4.0]undec-7-ene (99%), aluminum hydroxide, 3-bromopropionic acid

(97%), ethyl acetate (99.8%) and acetonitrile (99.8%) were bought from Sigma-Aldrich.

Tetrabutylammonium bromide and all of the epoxides unless otherwise specified were

bought from Aladdin Reagent Co. Glycidyl phenyl ether was bought from TCI Shanghai.

All of the solvents and chemicals were bought from Sigma-Aldrich, and were used without

further purification.


DILA was synthesized by two-step method. Firstly, DBPILs was prepared according

to our previous work. In a typical reaction, the chosen amount of 3-bromopropionic acid

was dissolved in ethyl acetate, then 2 equivalents of DBU was dropped into the flask. The

mixture was stirred for an hour at room temperature. After the reaction, the residue solid

was separated by filtration, and washed three times with ethyl acetate. The obtained

DBPILs was dried at 50oC for 24 h under vacuum. DILA was synthesized by DBPILs and

79 | P a g e

aluminum hydroxide in a hydrothermal reactor. Amount of aluminum hydroxide and 2 eq.

of DBPILs were added into a flask. Then water was poured into the flask. The mixture

was stirred and heated at 100 oC for 24 hours under reflex condition. After the reaction,

the residue solid was removed by filtration, and the water was removed by reduced

pressure distillation. Finally, DILA was obtained by recrystallized using as acetonitrile as

a solvent.

4.2.3 Characterization

Fourier transform infrared (FT-IR) spectra were recorded on a Thermo Nicolet 380

spectrophotometer with anhydrous KBr as standard (Thermo Electron Co.). NMR spectra

were recorded on a Bruker AVANCE III HD 300 spectrometer with DMSO-d6 as solvent.

4.2.3.1 Characterization of the catalysts

DBPILs-a

Figure 4.2 1H NMR of DBPILs-a

80 | P a g e

Figure 4.3 13C NMR of DBPILs-a

DILA

81 | P a g e

Figure 4.4 1H NMR of DILA

Figure 4.5 13C NMR of DILA

4.2.3.2 Characterization of the cyclic carbonates

Spectra of product 1H NMR and 13C NMR of Products

3a:

1H NMR ((CDCl3, TMS, 400 MHz): 3.84 (d, J = 6.0 Hz, 2H), 4.05 (t, J = 8.4 Hz, 1H),

4.60 (t, J = 8.0 Hz, 1H), 5.07–5.10 (m, 1H). 13C NMR (CDCl3, TMS, 100 MHz): 44.15,

70.46, 73.51, 154.94.

3b:



70.46, 73.51, 154.95.

3c:

82 | P a g e

1H NMR (CDCl3, TMS, 400 MHz): 0.88 (t, J = 7.5 Hz, 1H), 1.32 (dq, J = 14.8, 7.4 Hz,

2H), 1.42 – 1.56 (m, 2H), 3.46 (t, J = 6.5 Hz, 2H), 3.56 (dd, J = 11.5, 4.2 Hz, 1H), 3.63

(dd, J = 11.5, 2.7 Hz, 1H), 4.25 (dd, J = 8.3, 5.9 Hz, 1H) 4.52 (t, 3J = 8.4 Hz, 1H), 4.91

(dddd, J = 8.6, 6.0, 4.1, 2.8 Hz, 1H), 13C NMR (CDCl3, TMS, 100 MHz): 13.55, 18.63,

31.06, 66.00, 69.52, 70.54, 75.48, 154.88.

3d:

1H NMR (CDCl3, TMS, 400 MHz): 3.63 (dd, J = 4.0, 11.2 Hz, 1H), 3.70 (dd, J = 4.0,

11.2 Hz, 1H), 4.02–4.11 (m, 2H), 4.41 (dd, J = 6.4, 8.0 Hz, 1H), 4.51 (dd, J = 8.4, 8.4 Hz,

1H), 4.79–4.85 (m, 1H), 5.22–5.32 (m, 2H), 5.83–5.93 (m, 1H); 13C NMR (100 MHz,

CDCl3) δ 65.9, 68.6, 72.0, 75.0, 117.1, 133.5, 154.8.

3e:

1H NMR (CDCl3, TMS, 400 MHz): 4.34 (t, 1H, J = 8.4 Hz); 4.80 (t, 1H, J = 8.4 Hz);

5.68 (t, 1H, J = 8.0 Hz); 7.35–7.44 (m, 5H); 13C NMR (CDCl3, TMS, 100 MHz): 71.10,

77.92, 125.81, 129.12, 129.63, 135.70, 154.81

3f:

1H NMR (CDCl3, TMS, 400 MHz): 2.13 (s, 3H), 4.18 (dd, J = 11.2, 3.5 Hz, 1H), 4.27

(dd, J = 11.2, 2.4 Hz, 1H), 4.47 (dd, 3J = 8.4 Hz, 5.2Hz, 1H), 4.64 (t, 3J = 8.5 Hz, 1H),

5.17 (m, 1H), 6.88 (td, J = 7.4, 0.8 Hz, 1H), 6.93 (d, J = 7.8 Hz, 1H), 7.14-7.17 (m, 2H).

13C NMR (CDCl3, TMS, 100 MHz): 15.49, 66.17, 68.84, 74.11, 114.57, 121.92, 129.62,

154.65

3g:

1H NMR (CDCl3, TMS, 400 MHz): 4.15 (dd, 3J = 4.4 Hz, 2J = 10.8 Hz, 1H), 4.24 [dd,

3J = 3.6 Hz, 2J = 10.8 Hz, 1H), 4.55 (dd, 3J = 8.4 Hz, 2J = 6 Hz, 1H), 4.62 (t, 3J = 8.4 Hz,

1H), 5.03 (m, 1H), 6.91 [d, 3J = 8.0 Hz, 2H), 7.08 (s, 1H), 7.31 (t, 3J = 8.0 Hz, 2H). 13C

NMR (CDCl3, TMS, 100 MHz): 66.17, 68.84, 74.11, 114.57, 121.92, 129.62, 154.65

3h:

83 | P a g e

1H NMR ((CDCl3, 400 MHz): 1.33-1.54 (m, 2H), 1.57-1.74 (m, 2H), 1.81-2.2 (m, 4H),

4.59 -4.77(m, 2H). 13C NMR (CDCl3, TMS, 100 MHz): 19.18, 26.81, 75.74, 155.45.

3h:

1H NMR (CDCl3, TMS, 400 MHz): 1.52 – 1.55 (m, 2H), 3.46 (t, J = 5.9 Hz, 2H), 3.55

(dd, J = 11.5, 4.2 Hz, 1H), 3.63 (dd, J = 11.5, 2.7 Hz, 1H), 4.25 (dd, J = 8.2 5.9 Hz, 1H)

4.52 (t, 3J = 8.4 Hz, 1H), 4.91 (dddd, J = 8.6, 5.9, 4.2, 2.8 Hz, 1H), 13C NMR (CDCl3,

TMS, 100 MHz): 25.60, 66.09, 69.51, 70.55, 75.50, 154.93.



Schlenk tube with a magnetic stirrer. In a typical reaction, 0.5ml of epoxides and chosen

amounts of catalyst were added into the reactor. Then, a balloon of CO2 was connected

to the schlenk tube, controlling the temperature within the desired range afterwards. After

the reaction, the remaining CO2 was vented out slowly. The yield of the products was

characterized by HNMR spectroscopy of the crude reaction mixture on a Bruker AVANCE

III HD 300 spectrometer by using CDCl3 as solvents.

4.2.5 Recycle experiment

After the reaction, 10 ml ethyl acetate was poured in to the schlenk tube, the ionic

liquids catalyst precipitated from the mixture, and then catalyst was separated from the

mixture by filtration and washed three times with ethyl acetate. Afterwards, the catalyst

was dried at 50 oC for 24 h in oven, and ready for the recycling experiment. The liquid

phase was dried at 80 oC by vacuum distillation, afterwards the product can be obtained.

The yield of the product was calculated by weight.



It has been proven that Br- is an excellent nucleophilic ion for the cycloaddition

reaction in our previous work.[145,223] Br- is chosen as a model ion for this reaction. After

the catalysts were synthesized, their activities were investigated via the cycloaddition

84 | P a g e

reaction of epichlorohydrin with CO2 to synthesize chloropropene carbonate (CPC) in a

schlenk tube at 30 °C, and the corresponding results were displayed in Table 4.1. As a

raw material of DILA, Al(OH)3 and BrC2COOH showed no CPC produced in catalyzing

the reaction under this room temperature and 1bar CO2 condition (Entry 1, 2). The reason

maybe that Al(OH)3 cannot dissolved in epichlorohydrin and BrC2COOH cannot

dissociate Br-. TBAB was reported as a co-catalyst that widely used the cycloaddition

reaction of CO2 with epoxide, and it only exhibited a 19% yield of CPC at this mild

condition.

Table 4.1: Reactions of CO2 with epichlorohydrin catalyzed by different ILsa

Entry Catalyst Time (h) Yieldb (%) TOF (h-1)

1 Al(OH)3 6 trace ---

2 c BrC2COOH 6 trace ---

3 TBAB 6 19 0.5

4 DBPILs-a 6 73 2.0

5 DILA 6 94 2.7

6d DILA 2 60 7.5

aReaction conditions: epichlorohydrin (0.5ml), ILs (6 mol%), 1 bar of CO2 (balloon), Temperature

(30oC). bDetermined by 1H NMR spectroscopy of the crude reaction mixture. c BrC2COOH = 3-

bromopropionic acid, TBAB = Tetrabutylammonium bromide. d Catalyst (4 mol %), e Catalyst (25

mol %). TOF = turn over frequency = mol of CPC generated per mol catalyst and per hour.

For comparison purpose, DBPILs-a with a protic acid was synthesized and

investigated (entry 4). DBPILs-a showed a much higher yield of CPC (73%) than TBAB

(Entry 4 vs entry 3). Based on our previous work, the possible reason was that DBPILs-

a had a strong H-bond interaction with epoxide, which made the ring open of

epichlorohydrin much easier. Then, DILA was prepared and used for this reaction at the

same conditions, and it displayed a 94% yield of CPC within 6 hours (Entry 7), the highest

CPC yields of all the catalysts at room temperature and 1bar CO2 pressure. To our

surprise, when we reduce the reaction time to 2 hours and the dose of catalyst to 4%, the

catalyst DILA showed a 60% yield of CPC with a TOF of 7.5 (Entry 6). The high activity

maybe caused by the activation of epoxides by the powerful aluminum ion and

nucleophilic bromide ion.

85 | P a g e


Figure 4.6 Effects of reaction time under different temperature. Reaction conditions:

epichlorohydrin (0.5 ml), catalyst dose (4%), 1 bar CO2 (balloon).

The effect of reaction time was investigated with different temperature under a

catalyst dose of 4% and 1 bar of CO2 (Figure 4.6). It could be obviously seen that the

CPC yield increased with the increasing of reaction time and temperature. It displayed

83%, 91% and 99% yields of CPC within 6 hours at 25 oC, 30 oC and 50 oC separately.

In the initial of the reaction, the yield of CPC is almost linear. However, the reaction rate

will decrease with the increasing of CPC, and the yield of CPC goes to a slow growth

stage. The possible reason maybe that the producing of CPC result in the viscosity of

reaction system increased, which affect the transferring effect of CO2 in the liquid phase.

Considered that the yield of CPC is almost liner in initial of the 2 hours at 25 oC and 30oC,

2 hours are chosen as the best time for the next studies.

The effect of catalyst dose on the reaction was investigated under the 30oC and

balloon of CO2 within 2 hours (Figure 4.7). It could be seen that the catalyst amount

showed great effect on CPC yield. The increase of catalyst dose resulted in an obviously

increase in CPC yield under a catalyst amount level of 1% - 5%. But the further increasing

amount of catalyst exhibited negative influence on CPC yield (1% - 5%). It could be

explained that, when catalyst dose is higher than 5%, the viscosity of reaction system will

increase quickly with the increasing of DILA at this room temperature, and result in the

0 1 2 3 4 5 6

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30 oC

50 oC

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negative effect of transferring CO2 in liquid phase. The results indicated that adopting

appropriate catalyst dose had significant impact on the cycloaddition reactions. Therefor,

5% was chosen as the optimal catalyst loading for the next study.

Figure 4.7 Effects of catalyst dose. Reaction conditions: epichlorohydrin (0.5ml), 1 bar CO2

(balloon), temperature (30oC), reaction time (2 h).

Figure 4.8 Effects of temperature. Reaction conditions: epichlorohydrin (0.5ml), CO2 (balloon),

catalyst dose (5%), time (2 h).

0 1 2 3 4 5 6 70

20

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80

Catalyst dose (%)

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25 30 35 40 45 50

40

50

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70

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90

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Temperature (oC)

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The effect of reaction temperature on the cycloaddition reaction was investigated

under 30oC and 1 bar of CO2 within 2 hours. As shown in Figure 4.8, the yield of CPC

increased linearly when temperature went up. DILA exhibited a good CPC yield within 2

hours (58%) even at 25oC. When temperature increased to 50oC, DILA showed a 90%

yield of CPC at 1 bar CO2 within 2 hours, which was promising in the industrial application.


Subsequently, a range of different substituted terminal epoxides were examined

under 1 bar of CO2 in the presence of DILA within 5 hours. Taking into account of the

industrial application, the reaction temperature was chosen as 50oC for the study. The

isolated yields of the target cyclic carbonates were determined by 1H NMR of the crude

reaction mixture. The result was exhibited in Table 4.2. In general, all of the terminal

epoxides showed excellent yields of corresponding carbonates (> 95%) under this mild

condition except the carbonate 3h. Only 72% yield of 3h obtained after 5 hours reaction.

This may be caused by the high stereo-hindrance effect.

Table 4.2: Reaction of CO2 with substrates catalyzed by DILAa

3a: 99% 3b: 99% 3c:95%

3d: 99% 3e: 95% 3f: 97%

3g: 96% 3h: 72%

aYield were determined by HNMR of the crude reaction mixture.

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Figure 4.9 Recycle experiment catalyzed by DILA. aReaction conditions: 2g (0.5ml), DILA (5

mol%), 1 bar of CO2 (99.995%, balloon), temperature (50oC), reaction time (5 h).

Recycle experiments were also conducted to examine the stability of the catalyst

DILA for the fixation of CO2 with epoxides. 2f was chosen as an optimal terminal epoxide

to study the cycling performance of DILA for the easy separation by adding ethyl acetate.

The results displayed in Figure 4.9 showed that the catalyst DILA could be reused for at

least 4 runs without any obviously decrease of catalytic activity.

4.3.5 Probable mechanism

Based on the previous reports and the results above, we proposed a possible

mechanism for chemical fixation reaction of CO2 into cyclic carbonate catalyzed by

catalyst DILA (Scheme 4.2). Firstly, aluminium ion of DILA can activate epoxide and make

the C-O bond of epoxide polarized, which led to the ring opening of epoxide easier. Then,

the nucleophilic attack of Br- on less sterically hindered carbon atom of the epoxide

caused the ring opened and transforms into intermediate B. Subsequently, the negative

ions of oxygen of the catalyst coordinated with CO2 to form complex C. Nucleophilic attack

of O- on the carbamate salt produced the alkyl carbonate D. Finally, the cyclic carbonate

is obtained by ring-closure step and the catalyst DILA is regenerated.

1 2 3 4

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Scheme 4.2. Probable mechanism of the cycloaddition reaction catalyzed by DILA.

4.4 Conclusions:

In summary, a powerful DILA with nucleophilic site and aluminum ion was

synthesized and successfully used as a single-component catalyst in the cycloaddition

reaction of CO2 with epoxides at 1 bar CO2 and very mild temperature (25-50oC). It

showed excellent activity under this mild condition and was found to be applicable to

various epoxides. Furthermore, the catalyst could be reused at least four times without

any obviously decrease of catalytic activity. A possible mechanism of ring-opening of

epoxide assisted by aluminum ion and activation of CO2 induced by negative ions of

oxygen was proposed. This work provides a highly efficient and recycling aluminum

containing ionic liquids for conversion of CO2 with epoxide at very mild condition, which

is promising for the applications of CO2 conversion.

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Chapter 5: Poly Ionic Liquids Based Membranes as Highly

Efficient Heterogeneous Catalyst for Conversion of CO2 to

Cyclic Carbonate under Mild Conditions

5.1 Introduction

The combination of high activity and easy recovery of catalysts is recognized as a

great challenge in catalysis research from an industrial point of view.[237] The reported

homogeneous catalysts are usually more efficient, while it is costly to reclaim them from

reaction products. By contrast, heterogeneous catalysts can be easily separated from the

products and reused. But they are inefficient, and at the same time, high temperatures

and pressures are often demanded, which make them expensive. This has promoted the

development of efficient strategies for homogeneous catalysis and heterogeneous

separation.[175,176]

The efficient conversion of CO2 with epoxide to produce cyclic carbonate at mild

conditions still remains an important issue. To this end, various catalysts have been

developed for the synthesis of cyclic carbonates under mild conditions of ambient CO2

pressure and/or room temperature. In the respect, we also synthesized a series of well-

designed ionic liquids and used as highly efficient homogenous catalyst for this reaction

in our previous works. Although the ionic liquids catalyst showed excellent yields of cyclic

carbonate at room temperature and 1 bar CO2, which made this reaction promising

energy saving process. The separation of ionic liquids catalyst and cyclic carbonate is

inconvenient, and distillation process is always needed, which led to the increasing of the

energy input. On the basis of the problems in homogeneous catalytic processes, some

heterogeneous catalysts have been developed for chemical conversion of CO2 to cyclic

carbonates under mild conditions. In contrast, heterogeneous systems are easier to

separate, but they are inefficient and long reaction time, large amount loading of catalyst

and co-catalyst hard reaction conditions are always needed. Hence, it is highly necessary

to explore a convenient approach to realize both high activity and quick separation of

catalysts.

Recently, Gao group[238] reported a kind of cross-linked poly(ionic liquid)s (PILs)

with swelling property to increase catalytic activities of heterogeneous catalysts. The

swelling property could promote the contact of nonporous PILs with substrates. The

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swelling PILs were successfully utilized for the reaction of 2-(arylamino) ethanol and

ethylene carbonate (EC), and showed excellent catalytic activities, which was similar to

homogeneous ionic liquid monomers. Gao group[239] synthesized another PILs by

polymerization of N-vinylimidazolium with divinylbenzene (DVB) and they were utilized in

the reaction of 2-(phenylamino) ethanol (2-PAE) and EC. It was found that the PILs

exhibited even better catalytic performance than homogeneous catalyst 1-butyl-3-methyl-

imidazolium acetate (BmimOAc) because of the swelling property and selective

absorption.

In spired by this, we synthesized a series of cross-linked poly (vinylimidazole/butyl

acrylate) ionic liquids membranes (PVBILs). The PVBILs were successfully used as a

heterogeneous catalyst in the cycloaddition reaction of CO2 with epoxide to produce cyclic

carbonate under mild conditions. The best PVBILs showed a 90 % yield of chloropropene

carbonate (CPC) in 24 hours with a catalyst loading of 2 % at 50 oC and 1 bar of CO2.

The high activity was even better than homogenous catalyst, because of the good

swelling property and CO2 solubility of PVBILs. The using of cross-linked PVBILs

membranes for the cycloaddition reaction of CO2 with epoxide to produce cyclic

carbonate supply an efficient way to combine activity and recovery of catalysts, which is

benefit for energy-saving and industrial applications.


5.2.1 General information

Carbon dioxide was supplied by Air Liquide Danmark with a purity of 99.995%.

Chemicals and solvents such as butyl acrylate, N-vinylimidazole, azodiisobutyronitrile

(AIBN), dimethylformamide (DMF), CDCl3, 1, 6-dibromohexane, 1-bromobutane, 1-

bromoethanol and all of the epoxides unless otherwise specified were bought from

Sigma-Aldrich and were used without further purification.

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5.2.2 Synthesis of catalyst used in this study.

5.2.2.1 Preparing of PVBILs

Scheme 5.1 Two step for the synthesis of PVBILs (Step 1 synthesis of copolymers)

The PVBILs were prepared by two step method based on the report. [240] Here,

copolymers poly (Vim/BuA n:m = 1:1) was chosen to show the synthetic process (Scheme

5.1). In a typical reaction, 0.53 mmol of AIBN was dissolved in DMF (10 mL) in a 100 ml

flask, and then monomers 1-vinylimidazole (20 mmol) and butyl acrylate (20 mmol) were

added into the flask. After remove all traces of air by bubbling nitrogen for 20 min, the

mixture was stirred for 10 h at 70°C under nitrogen conditions. When the reaction was

finished, the crude product could be precipitated by adding of ether, and then purified by

recrystallization method using EtOH as a solvent. Finally, the obtained product was dried

in vacuum oven for 24 hours. Other copolymers were synthesized in the same way by

changing the ratio of VIm-co-BuA.

Scheme 5.2 Two step for the synthesis of PVBILs (Step 2)

After copolymers were obtained, PVBILs were prepared based on reported

literature.[240] Here, PVBILs 1h was chosen to show the synthetic process (Scheme 5.2).

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In a typical reaction, the obtained copolymer poly (VIm-co-BuA n:m = 3:7) (1.5 g, n=3.0

mmol) was dissolved in ethanol (12 mL) by stirring overnight. Then, 1,6-dibromohexane

(0.12 g, 0.5 mmol) and 1-bromobutane (0.13 g, 1 mmol) were added in to the mixture.

The mixture solution was degassed by ultrasonication for 10 min and solvent-casted in a

Teflon petri dish. Put the casting solution to remove entrapped residues of solvent at room

temperature. The cast membrane was dried in vacuum oven for 12 hours at 65 oC. Finally,

the obtained PVBILs membranes were ground into small particles in liquid nitrogen for

using. Other PVBILs were synthesized in the same way by changing the ratio of the

reactant.

5.2.2.2 Preparing of Poly [VBIM][Br] (PVIMBr)

Scheme 5.3 Synthesis of PVIMBr by two steps

PVIMBr was synthesized by two-step method based on the reported literature[144]

(Scheme 5.3). In a typical reaction, 1-vinylimiazole (5 g, 53 mmol) and AIBN (0.087 g,

0.53 mmol) were dissolved in DMF (10 mL), the reaction was conducted at 80 oC under

the protection of nitrogen. After 12 hours reaction, the mixture was cool to room

temperature. A brown solid poly (VIm) was obtained by adding of acetone. Wash product

three times by acetone. Then poly (VIm) (0.25 g, 2.6 mmol) and 1-bromobutane (0.64 g,

2.6 mmol) were dissolved in ethanol (12 mL), and casting the solution in a small Teflon

petri dish (5*5 cm). Put the casting solution to remove entrapped residues of solvent at

room temperature. The cast membrane was dried in vacuum oven for 12 hours at 70 oC.

Finally, the obtained PVIMBr were ground into small particles in liquid nitrogen for using.

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5.2.2.3 Preparing of Poly(butyl acrylate) (PBA)

Scheme 5.4 Synthesis of PBA

PBA was prepared in accordance with the general polymerisation procedure

(Scheme 5.4). In a typical reaction, butyl acrylate (5.12 g, 40 mmol) and AIBN (0.087 g,

0.53 mmol) were dissolved in DMF (10 mL). The product polymer was reclaimed as a

transparent liquid with high viscosity after precipitation into DI water.

5.2.3 Characterization

Fourier transform infrared (FT-IR) spectra were recorded on a Thermo Nicolet 380

spectrophotometer with anhydrous KBr as standard (Thermo Electron Co.). NMR spectra

were recorded on a Bruker AVANCE III HD 300 spectrometer with DMSO-d6 as solvent.

5.2.3.1 Characterization of the catalysts

Poly(vinylimidazole)

Yield > 65%. Tg=164.2°C. IR (cm-1): 3111cm-1 (C=C-H stretching), 1660 cm-1 (C=N

stretching), 1494 cm-1 (N=C-H stretching), 1282 cm-1 and 1230 cm-1 (ring vibrations), 914

cm-1 (C-H out of plane bending), 662 cm-1 (ring torsion), 634 cm-1 (C=C-H and N=C-H

wagging). 1H-NMR (1H, ppm, DMSO-d): 7.49-6.62 (m, 3H), 3.24-2.78 (m, 1H), 1.96 (s,

2H)

PVIMBr

Yield > 65%, Tg= 164.2 oC. IR (cm-1): 3111cm-1 (C=C-H stretching), 1660 cm-1 (C=N

stretching), 1494 cm-1 (N=C-H stretching), 1282 cm-1 and 1230cm-1 (ring vibrations), 914

cm-1 (C-H out of plane bending), 662 cm-1 (ring torsion), 634 cm-1 (C=C-H and N=C-H

wagging). 1H-NMR ( H, ppm, DMSO-d): 7.49-6.62 (m, 3H), 3.24-2.78 (m, 1H), 1.96 (s,

2H)

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PBA

Yield > 65%, Tg= -47.4oC. IR (cm-1): 3011-2827 cm-1, 1451cm-1 and 1381cm-1 (-CH2-

symmetric and asymmetric stretching), 1727 cm-1and 1154 cm-1 (stretching vibration C=O

and C-O-C in acrylate group). 1H-NMR ( H, ppm, CDCl3): 3.96 (m, 2H), 2.39-1.44 (m, 3H),

1.56 (m, 2H), 1.31 (m, 2H) 0.87(m, 3H).

Poly(Vim/BuA n:m = 1:1)

IR (cm-1): 3111cm-1 (C=C-H), 3012-2844 cm-1, 1451cm-1 (-CH2-), 1727 cm-1 and

1160 cm-1 (C=O and C-O-C in acrylate group), 1494 cm-1 (N=C-H), 1267 cm-1 and

1223cm-1 (ring), 912 cm-1 (C-H), 664 cm-1 (ring), 632 cm-1 (C=C-H and N=C-H); 1H-NMR

(1H, ppm, CDCl3): 7.4-6.4 (m, 3H), 4.1-3.5 (m, 2H), 2.27-1.45(m, 6H), 1.46 (m, 2H), 1.26

(m, 2H), 0.87 (m, 3H).

Poly (Vim/BuA n:m = 3:7)

IR (cm-1): 3111cm-1 (C=C-H stretching), 3012-2844 cm-1, 1451cm-1 (-CH2- symmetric

and asymmetric stretching), 1722 cm-1and 1160 cm-1 (stretching vibration C=O and C-O-

C in acrylate group), 1494 cm-1 (N=C-H stretching), 1267 cm-1 and 1223cm-1 (ring

vibrations), 912 cm-1 (C-H out of plane bending), 664 cm-1 (ring torsion), 632 cm-1 (C=C-

H and N=C-H wagging); 1H-NMR (ppm, CDCl3): 7.4-6.4 (m, 3H), 3.96 (m, 2H), 2.35-1.62

(m, 6H), 1.52 (m, 2H), 1.27 (m, 2H) 0.86(m, 3H).

Poly (Vim/BuA n:m = 7:3)

IR(cm-1): 3112cm-1 (C=C-H stretching), 3012-2800 cm-1, 1455cm-1 (-CH2- symmetric

and asymmetric stretching), 1722 cm-1and 1164 cm-1 (stretching vibration C=O and C-O-

C in acrylate group). 1663 cm-1 (C=N stretching), 1494 cm-1 (N=C-H stretching), 1275 cm-

1 and 1227cm-1 (ring vibrations), 912 cm-1 (C-H out of plane bending), 664 cm-1 (ring

torsion), 636 cm-1 (C=C-H and N=C-H wagging); 1H-NMR ( ppm, DMSO-d): 7.52-6.62 (m,

3H), 4.05-3.55 (m, 2H), 2.27-1.45(m, 6H), 1.45 (m, 2H), 1.24 (m, 2H) 0.87(m, 3H).

5.2.3.2 Characterization of the cyclic carbonates

Spectra of product 1H NMR and 13C NMR of Products


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70.46, 73.51, 154.94.




NMR (CDCl3, TMS, 100 MHz): 66.17, 68.84, 74.11, 114.57, 121.92, 129.62, 154.65



Schlenk tube with a magnetic stirrer. In a typical reaction, 0.5ml of epoxides and chosen

amounts of catalyst were added into the reactor. Then, a balloon of CO2 was connected

to the schlenk tube, control the temperature within the desired range afterwards. After the

reaction, the remaining CO2 was vented out slowly. The yield of the products was

characterized by HNMR spectroscopy of the crude reaction mixture on a Bruker AVANCE

III HD 300 spectrometer by using CDCl3 as solvents.

5.2.5 Swelling ratio measurement

The swelling property was evaluated by calculating the swelling ratio. First, record

the weights of dry membranes by an electronic balance. Then catalyst membrane used

in this study was immersed in the ethanol until the weight was constant. Finally calculate

the swelling ratio by following equation. Swelling ratio = (Ww - Wd) /Wd

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Figure 5.1 Catalyst used in this study.

The structures of the catalysts used in this study were displayed in Figure 5.1. After

the catalysts were synthesized, the swelling ratio of the catalyst used in this study was

tested first by using ethanol as a solvent instead of epoxide, because of the toxic of the

epoxide. Their activities were also investigated via the cycloaddition reaction of

epichlorohydrin with CO2 to synthesize chloropropene carbonate (CPC) in a schlenk tube

at 50 °C. The corresponding results were showed in Table 5.1.

It has been proven that Br- is an excellent nucleophilic ion for the cycloaddition

reaction in our previous work.[145,223] Herein, catalyst loading is based on per unit of

bromide. As shown in Table 1, both PBA and PVIMBr had no swelling ability. PBA had

no catalytic activity at this mild condition (Entry 1), because it has no nucleophilic bromide

ion to activate epoxide. PVIMBr was reported an efficient heterogeneous catalyst for

cycloaddition reaction of CO2 and epoxide at 130 oC and 2 MPa CO2 pressure. However,

it only showed 2 % yield of CPC with 12 hours reaction under 50 oC and 1 bar CO2 (Entry

2).

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Table 5.1 Catalyst screening for conversion of CO2 to CPC

Entry Catalyst Swelling (wt%) Yieldb (%)

1 PBA ---- 0

2 PVIMBr ---- 2

3 1a 48 19

4 1b 58 39

5 1c 66 52

6 1d 123 68

7 1e 120 54

8 1f 162 76

9c 1f 162 90

aReaction conditions: epichlorohydrin (1 ml), catalyst (2 mol%), 1 bar of CO2 (balloon), Temperature

(50 oC), Time (12 h). bDetermined by 1H NMR spectroscopy using CDCl3 as a solvent. cTime (24 h).

To our surprise, PVBILs 1a with a swelling ratio of 48 % showed a 19 % yield of CPC

at the same conditions (Entry 3). When compared the PVBILs that with same groups but

different swelling ratio, we found the ratio of vinylimidazole (VIM) and butyl acrylate (BA)

could affect the swelling ability. The order of swelling ratio is 1c >1b>1a (Entry 5 vs 4 and

3), which indicate that the swelling ability ratio increase with the decreasing of the ratio of

VIM:BA. Furthermore, the catalytic activity was well consistent with the swelling ability,

and 1c showed highest activity of these three catalysts, 52 % yield of CPC could be

obtained in 12 hours. The same behaviour was also found in the other PVBILs catalysts

used in this study. However, 1d displayed much higher activity than 1e, even they had a

similar swelling ratio (Entry 6 vs 7). The possible reason maybe that 1d had imidazole

groups, which can activate CO2 efficiently and led to the high activity. Based on our

previous work, the hydroxyl group could activate epoxide through hydrogen-bond

interaction with epoxide and made the ring open of epichlorohydrin much easier.

Therefore, PVBILs 1f containing hydroxyl groups and imidazole groups was prepared and

used for this reaction at the same conditions. PVBILs 1f showed the highest yield of CPC

and swelling ability among all the catalysts (Entry 8 vs 1-7), because of the activation of

CO2 and epoxide by imidazole groups and hydroxyl groups. When we increased the

reaction time to 24 hours, the PVBILs 1f showed a 90 % yield of CPC at the same

conditions. Then 1f was chosen as a best catalyst for the next studies.

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0.5 1.0 1.5 2.0 2.5 3.0

0

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Catalyst dose (mol%)

Figure 5.2 Effects of catalyst loading (Epichlorohydrin:1 ml, 1 bar CO2, Temperature: 50°C,

Time: 12 h).

The effect of catalyst loading on the reaction was investigated under the 30oC and

balloon of CO2 within 12 hours (Figure 5.2). It could be seen that the catalyst amount

showed great effect on CPC yield. The increase of catalyst loading resulted in an

obviously increase in CPC yield under a catalyst amount level of 0.5 % - 2 %. But the

further increasing amount of catalyst exhibited negative influence on CPC yield (2% - 3%).

It is easy to understand the CPC yield increased with the increasing of catalyst loading at

catalyst amount level of 0.5 % - 2 %. And the decreasing part can be explained that,

epichlorohydrin will swelled in PVBILs during the reaction, because the amount of

epichlorohydrin is fixed, therefore the concentration of epichlorohydrin per Br- of the

PVBILs decreased with the increasing catalyst dose, which will reduce the interaction

between the epoxides and the activate site from PVBILs, and finally resulted in the

decreasing of catalytic activity. Too high catalyst loading did not benefit the cycloaddition

reaction catalyzed by PVBILs and adopting appropriate catalyst dose had significant

impact on the cycloaddition reactions. Therefore, the catalyst loading of 2 % was chosen

for the optimal catalyst dose for next study.

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0 3 6 9 12 15 18 21 24 27 30

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Time (h)

Figure 5.3 Effects of reaction time (Epichlorohydrin: 1 ml, 1 bar CO2, Temperature: 50°C,

Catalyst: 2 mol% per bromide unit).

The effect of reaction time was investigated with different temperature under a

catalyst dose of 2 % and 1 bar of CO2 (Figure 5.3). It could be obviously seen that the

CPC yield increased with the increasing of reaction time. In the initial of the reaction, the

yield of CPC is almost linear and reached to 82 % within 12 hours. However, the reaction

rate will decrease with the increasing of CPC, and the yield of CPC goes to a slow growth

stage. The possible reason maybe that CPC can not get out from PVBILs 1f during the

reaction, the producing of CPC will occupy a lot of reaction area, which will reduce the

interaction between epoxides and the activate sites of PVBILs, and finally resulted in the

decreasing of reaction rate. Considered that the yield of CPC is almost liner in initial of

the 9 hours at 30oC, 9 hours are chosen as the best time for the next studies.


Scheme 5.5. Reaction of CO2 with substrates catalyzed by 1f

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Subsequently, different substituted terminal epoxide glycidyl phenyl (EGP) ether was

examined under 1 bar of CO2 and 50 oC in the presence of 1f. The isolated yields of the

target cyclic carbonates were determined by 1H NMR of the crude reaction mixture.

However, 1f only showed a 28 % yield of corresponding cyclic carbonate after 25 hours

reaction at this mild condition (Scheme 5.5). The possible reason maybe that, the swelling

ability of 1f for EGP is low because of the big molecular structure of EGP compared to

epichlorohydrin, based on the above study, the low swelling ability can reduce the

catalytic activity sharply.


Figure 5.4 Photograph shows the different of catalyst 1f before and after reaction

Recycle experiments were conducted to examine the stability of the catalyst 1f for

the fixation of CO2 with epichlorohydrin to produce CPC. After the reaction, catalyst 1f

could be recovered by adding of ethanol and filtration. However, the yield of CPC

decreased from 76% to 52% after 2 runs, and the colour of the catalyst changed from

white and transparent to canary yellow (Figure 5.4). The decreased yield of CPC maybe

caused by the side-reaction. Another reason maybe that, there are still some CPC or

epichlorohydrin left in the recovered 1f because of the swelling, which will reduce the

swelling ability of 1f and result in the decreasing catalytic activity of 1f. Further studies

will be focus on the characterisation of recovered catalyst 1f to find the mechanism of the

decreasing catalytic activity during the recycling experiment.

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5.3.5 Probable mechanism

Scheme 5.6 Probable mechanism of the cycloaddition reaction catalyzed by DILA.

Based on the previous reports and the results above, we proposed a possible

mechanism for chemical fixation reaction of CO2 into cyclic carbonate catalyzed by

catalyst 1f (Scheme 5.6). Firstly, hydroxyl group of 1f can activate epoxide and make the

C-O bond of epoxide polarized, which led to the ring opening of epoxide easier. Then, the

nucleophilic attack of Br- on less sterically hindered carbon atom of the epoxide caused

the ring opened and transforms into intermediate B. Subsequently, the imidazole nitrogen

of the catalyst coordinated with CO2 to form complex C. Nucleophilic attack of O- on the

carbamate salt produced the alkyl carbonate D. Finally, the cyclic carbonate is obtained

by ring-closure step and the catalyst 1f is regenerated.

5.4 Conclusions

In summary, a series of cross-linked poly (vinylimidazole/butyl acrylate) ionic liquids

membranes (PVBILs) were prepared and used as highly efficient heterogeneous

catalysts for fixation of CO2 with epoxide at mild conditions. PVBILs could show

comparable activities in the coupling of epoxide and CO2 with the traditional homogenous

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catalysts, because of the activity of CO2 and “homogeneous-surroundings” caused by

swellable properties. Swelling behaviour was studied and found to be consistent with the



show a 90% yield of carbonate within 24 hours at 50 oC and 1 bar of CO2. This work

provides a highly efficient way to combine the advantage of homogeneous catalyst and

heterogeneous catalyst, which is promising for the applications of CO2 conversion.

Note:

This part of work was cooperated with Ting Song. The synthesis, characterization of

the catalyst and the swelling experiment were done by Ting Song.

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Chapter 6: Biological Porphyrin Ionic Liquids as

Photocatalysts for Conversion of CO2 to Carbonates

6.1 Introduction

Carbon dioxide, well known as a global warming gas, is also regarded as an

abundant, nontoxic and renewable C1 resource. The utilization of CO2 as raw materials

for production of energy carriers and chemicals has been widely demonstrated. One of

the typical feasible routes is the synthesis of five-membered cyclic carbonates by

cycloaddition of CO2 with epoxides.

A large range of catalytic systems have been reported for the cycloaddition of

carbon dioxide to produce cyclic carbonates. Specially, ionic liquids (ILs) have obtained

much attention as both green solvent and catalyst for this reaction because its high

capability for CO2 capture and easy tuning basicity-nucleophilicity by simple design of the

IL structure. Although most of the ionic liquid catalyst systems show a good yield to

produce carbonates, high temperatures and high CO2 pressures are always needed,

which makes this process not so “sustainable”. Therefore, co-catalysts containing metal

ions are widely used to improve the catalytic performance of ILs under mild conditions.

Among all of the metal containing co-catalyst metalloporphyrins have received much

interest due to the unique framework structure of porphyrin. For example, Xiao and Meng

et al[153] reported a porphyrin based porous organic polymer (POP-TPP) for this

cycloaddition reaction of CO2. The catalytic activities of metalloporphyrins can be easily

adjusted by introducing different metal ions such as Co3+, Zn2+, and Mg2+. As

heterogeneous catalysts, these meatal based POP-TPP were very active for this reaction

at ambient conditions with the presence of TBAB. Diphenylporphyrin]manganese(III)

chloride / phenyltrimethylammonium tribromide [152] and bisimidazole-functionalized

porphyrin cobalt(III) complexes[154] were also reported for the cycloaddition of CO2 to

produce cyclic carbonate under mild conditions.

Most recently (In the year 2019), Jiang et al.[150] first reported the integration of

photothermal effect of carbon-based Zn-MIF materials for the cycloaddition of CO2 with

epoxide. The best catalyst showed 94 % yield of cyclic carbonate after 10 hours with the

presence of TBAB as co-catalyst and DMF as solvent under 1 bar CO2, 300 mW·cm-2

full-spectrum irradiation and ambient temperature. This work is the first report on

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integration of photothermal effect for the cycloaddition of CO2 with epoxide to produce

cyclic carbonate. As a biomimetic catalyst, metalloporphyrin could not only activate CO2

at atmospheric CO2 conditions, but also have a good capacity of visible light absorption.

Figure 6.1. Picture shows the synthesis of carbonates catalysed by bio-porphyrin ionic liquids

Inspired by these works, we designed a series of biological metalloporphyrin based

ionic liquids (MPIL) to combine the advantages of ionic liquid and metalloporphyrin

(Figure 6.1). These MPIL catalysts can activate the epoxide and make the key step much

easy. The activation of CO2 supported by the ionic liquid part and metal centre of

porphyrin helps to react with epoxide at atmospheric CO2 conditions. Furthermore, MPIL

have a good capacity of visible light absorption, thus can reduce the energy inputs greatly

by using the visible light and realize the efficient conversion of atmospheric CO2 to

carbonate at very mind conditions with a visible light.


Carbon dioxide was supplied by Air Liquide Danmark with a purity of 99.995%.

Chemicals such as Zinc 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (90%),

5,10,15,20-Tetra(4-pyridyl)-21H, 23H-porphine (97%), 1,2-Epoxy-3-phenoxypropane

(99%) 3-Bromopropionic acid (97%) and all solvents unless otherwise specified were

bought from Sigma-Aldrich and were used without further purification. Photochemical

visible-light lamp source TOP-X500 was purchased from TOPTION INSTRUMENT CO.,

LTD China.

106 | P a g e




Figure 6.2 [ZnTPPPA]+Br- precipitated from the solvents

Porphyrin-based ionic liquids catalysts were synthesized by one-step method.

[ZnTPPPA]+Br- was chosen as a model to show the process. In a typical reaction, Zinc

5,10,15,20-tetra(4-pyridyl)-21H, 23H-porphine (1.00 mmol) and 3-Bromopropionic acid

(6.00 mmol) were dissolved in 10 ml N,N-Dimethylformamide (DMF) in a 100 ml flask.

The mixture was heated and stirred for 24 hours at 120 oC. After the reaction, the mixture

was separated by filtration, then 50 ml of ethyl acetate was added to the liquid phase,

then [ZnTPPPA]+Br- precipitated from the solvents (see Figure 6.2). The crude

[ZnTPPPA]+Br- could be obtained by centrifugal separation method. Washed it three times

107 | P a g e

with ethyl acetate, and dry it at 60 oC for 24 h under vacuum. Finally, a green colour

powder product was obtained.


The morphology was observed through a scanning electron microscope (JEOL JSM

6700F). Fourier transform infrared (FT-IR) spectra were recorded on a Thermo Nicolet

380 spectrophotometer with anhydrous KBr as standard (Thermo Electron Co.). NMR

spectra were recorded on a Bruker AVANCE III HD 600 spectrometer with DMSO-d6 as

solvent.


Figure 6.3 Photographic image shows visible light equipment for the reaction

The procedure of the cycloaddition reaction of CO2 with epoxide with a visible light

was shown in Figure 6.3. The coupling reaction of carbon dioxide and epoxide was carried

out in a 100 mL photocatalytic reactor with a magnetic stirrer. In a typical reaction, 1 g of

epoxide and appropriate amounts of catalyst were charged into the reactor at room

temperature. Then, a balloon of CO2 was connected to the reactor. Control the spectrum

108 | P a g e

irradiation within the desired range afterwards. After the reaction, the remaining CO2 was

vented out slowly, 10 ml ethyl acetate was added to the mixture, the liquid phase was

separated from catalyst by centrifugal method, then remove ethyl acetate by reduced

pressure distillation. After10 ml of water was added, products would precipitate from the

solvents, and then dried at 60 oC for 24 h under vacuum. The yield of the products was

characterized by weighing method.

6.3.4 Characterization of the catalysts and cyclic carbonates

Characterization of the catalysts

[ZnTPPPA]+Br-

Figure 6.4 1H NMR of [ZnTPPPA]+Br-

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Figure 6.5 SEM of the [ZnTPPPA]+Br-

Figure 6.6 UV spectrum of the [ZnTPPPA]+Br-

Spectra of product 1H NMR and 13C NMR of Products:




NMR (CDCl3, TMS, 100 MHz): 66.17, 68.84, 74.11, 114.57, 121.92, 129.62, 154.65

200 300 400 500 600

Ab

sorb

an

ce (

a.u

)

(nm)

110 | P a g e


Figure 6.7 Strctures of catalyst used in this study

We have been proved that Br- is an excellent nucleophilic ion for the cycloaddition

reaction in our previous work. Hence, Br- is chosen as the model anion. At the initial of

our study, we prepared a series of catalysts by one step method. The structure was

shown in Figure 6.7. The surface appearance of the [ZnTPPPA]+Br- was analyzed by

SEM (Figure 6.5). We can see that the [ZnTPPPA]+Br- is a long flatter ribbon-like fibre.

This may be greatly improving the energy transfer. The capacity of visible light absorption

of [ZnTPPPA]+Br- was studied by UV spectrum. As shown in Figure 6.6, there was a

strong signal at 420 nm, therefore, 420 nm-spectrum irradiation was conducted during

the experiment.

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Table 6.1: Reactions of CO2 with epoxide catalyzed by different catalystsa

Entry Catalyst Co-catalyst Visible light Time (h) Isolated yieldb

(%)

1c BrC2COOH -- No 24 0

2 TPP -- No 24 0

3 ZnTPP -- No 24 0

4 [ZnTPPPA]+Br- -- No 24 trace

5 [ZnTPPPA]+Br- -- No 48 3

6 [ZnTPPPA]+Br- -- Yes 20 21 aReaction conditions: epoxide (1.0 ml), catalyst (0.1mol%), CO2 (balloon), 150 W·m-2 visible-

spectrum irradiation (λ= 420 nm), room temperature.bIsolated yield was determined by

weighting method. cBrC2COOH=3-Bromopropionic acid.

Then, the catalytic activities of various porphyrin-based catalysts were carried out

with glycidyl phenyl (GP) and CO2 (balloon) under 420 nm-spectrum irradiation. The

results were shown in Table 6.1. It was found that all the raw materials used to synthesize

of MPILs had no catalytic activity at room temperature (Entries 1-3). However, there was

almost no products generated as catalysed by [ZnTPPPA]+Br- after 24 hours at room

temperature without the spectrum irradiation (Entry 4). When we increased the reaction

time to 48 hours, only 3% yield of CPC obtained (Entry 5). Then the activity of

[ZnTPPPA]+Br- was studied under a spectrum irradiation. To our surprise, [ZnTPPPA]+Br-

showed a 21% isolated yield of corresponding carbonate (Entry 6), which was promising

for realizing the high efficient conversion of CO2 to carbonate at very mind conditions.

Further studies about MPILs together with co-catalyst to improve the catalytic activity

were conducting.

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Conclusions and future work

In this project, we focused on the energy saving of cycloaddition reaction of CO2 with

epoxide to producing cyclic carbonate and the separation process of catalyst and

products. We designed a bunch of highly efficient ionic liquids catalysts for this reaction.

They could be used to catalyze the coupling of CO2 with epoxide under very mild

conditions without high energy input, such as room temperature and 1 bar CO2. An

efficient way to combine activity and recovery of catalysts was also developed for the

separation of ionic liquids catalysts and products. Furthermore, all the ionic liquids

catalysts showed high activity for this reaction. The major work and results for this

dissertation are summarized as follows:

1. A series of carboxylic acid–based functional ionic liquids (CABFILs) were facilely

prepared by one-step synthesis method. They displayed reversible temperature-

controlled phase transitions in PC, which was much useful for the coupling reaction and

separation processes. CABFILs were successfully used in reaction-separation for

conversion of CO2 to carbonates under metal- and solvent-free conditions. Besides, the

IL 3a displayed high activity, and nearly 92% PC yield was obtained within 20 min and

could be readily separated by filtration at room temperature for easy recycle. More

importantly, 3a was suitable for a variety of terminal epoxides. This approach helps to

avoid further waste of the subsequent separation step, as well as a highly effective way

to combine the benefits of heterogeneous and homogenous catalysts, which is of great

interest from the viewpoint of energy saving and chemical engineering.

2. We prepared DBPILs by introducing electron withdrawing groups to O-H acid. The

DBPILs with protonic acid and nucleophilic sites were used as single-component and

metal-free catalysts in the cycloaddition reaction of CO2 with epoxides at very mild

temperature and 1 bar CO2 conditions. DBPILs showed a great improvement of catalytic

activity and good substrate compatibility to various epoxides. Furthermore, DBPILs were

found suitable for the conversion of simulated flue gas. The results from experiments,

spectrum and DFT illustrated the activation of CO2 of DBPILs and strong H-bond

interaction between DBPILs and epoxide. This study provides a highly efficient epoxy

ring-open catalyst for transformation of CO2 with epoxide. The greatly improved catalytic

activity makes DBPILs a promising environmentally benign catalyst for the applications

of CO2 conversion at mild conditions.

3. A powerful DILA with nucleophilic site and aluminum ion was synthesized and

113 | P a g e

successfully used as a single-component catalyst in the cycloaddition reaction of CO2

with epoxides at 1 bar CO2 and very mild temperature (25-50oC). It showed excellent

activity under this mild condition and was found to be applicable to various epoxides.

Furthermore, the catalyst could be reused at least four times without any obviously

decrease of catalytic activity. A possible mechanism of ring-opening of epoxide assisted

by aluminium ion and activation of CO2 induced by negative ions of oxygen was proposed.

This work provides a highly efficient and recycling aluminium containing ionic liquids for

conversion of CO2 with epoxide at very mild condition, which is promising for the

applications of CO2 conversion.

4. A series of cross-linked poly(vinylimidazole/butyl acrylate) ionic liquids

membranes (PVBILs) were prepared and used as high efficient heterogeneous catalysts

for fixation of CO2 with epoxide at mild conditions. PVBILs could show comparable

activities in the coupling of epoxide and CO2 with the traditional homogenous catalysts,

because of the activity of CO2 and “homogenous-surroundings” caused by swellable

properties. Swelling behaviour was studied and found to be consistent with the



show a 90% yield of carbonate within 24 hours at 50 oC and 1 bar of CO2. This work

provides a highly efficient way to combine the advantage of homogeneous catalyst and

heterogeneous catalyst, which is promising for the applications of CO2 conversion.

5. A series of metalloporphyrin ionic liquids (MPILs) that combine the advantages of

ionic liquid and porphyrin were designed and synthesized by one step method. The

structure and surface appearance of these BPILs were investigated. These BPILs

catalysts have multiple active sites and a good capacity of visible light absorption due to

the advantages of functional ionic liquids and metal porphyrin part, thus can reduce the

energy inputs greatly by using the visible light. They were successfully used as a

photocatalyst in cycloaddition reaction of CO2 with epoxide to produce carbonate at room

temperature and 1 bar pressure under irradiation of a visible light.

In the future, we will still focus on the energy saving of cycloaddition reaction of CO2

with epoxide to producing cyclic carbonate and the separation process of catalyst and

products. Fixed bed reactor will be used to study PVBILs catalyzed cycloaddition reaction

of CO2 with epoxide. Clear energy such as visible light and electric will be induced as the

energy input to promote this reaction and realize the conversion of CO2 to cyclic

carbonate at very mild conditions.

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139 | P a g e

APPENDICES

The Cartesian coordinates for Chapter 2

C -

3.060394 -

2.010603 -

0.289510

A

C -

3.730399 -

0.878540 0.087082

C -

3.094583 0.400197 0.005711

C -

1.775153 0.406921

-0.528234

C -

1.171430 -

0.762297 -

0.881929

N -

1.791046 -

1.974263 -

0.764201

H -

1.165493 1.309452

-0.622426

H -

0.156713 -

0.775514 -

1.257683

C -

1.063810 -

3.221696 -

1.095193

H -

0.247143 -

2.944732 -

1.756378

H -

1.751377 -

3.869912 -

1.642896

C -

0.512175 -

3.956418 0.136807

H -

1.341489 -

4.399277 0.698996

H 0.083741 -

4.791413 -

0.244424

C 0.326805 -

3.118631 1.107816

H -

0.269769 -

2.312796 1.550098

H 0.642031 -

3.736616 1.952656

H -

3.519447 -

2.988727 -

0.227657

H -

4.742095 -

0.988023 0.447740

Br 0.674035 2.794755 -

0.296957

C 1.566110 -

2.465929 0.516085

O 1.799771 -

2.417869 -

0.678870

O 2.327959 -

1.934377 1.454464

H 3.081139 -

1.394207 1.056242

140 | P a g e

N -

3.711330 1.523442 0.413708

C -

5.095833 1.477991 0.879179

H -

5.402854 2.484849 1.152116

H -

5.772622 1.114657 0.098338

H -

5.198470 0.839737 1.762260

C -

3.092125 2.854848 0.305568

H -

3.447585 3.368872

-0.593560

H -

3.375142 3.438844 1.182333

H -

2.002575 2.803670 0.272862

C 3.952659 0.914970 0.016438

H 2.887619 1.141542 0.005955

C 4.428360 -

0.151681 -

0.868735

H 5.465475 -

0.156104 -

1.192899

H 3.725148 -

0.681837 -

1.503278

O 4.265292 -

0.418435 0.547486

C 4.842290 2.026140 0.491094

H 4.695148 2.901622 -

0.147131

H 4.576748 2.315311 1.510903

H 5.895015 1.733749 0.467078

C 2.707337 -

1.010979 2.188519

C 3.401140 -

0.999323 1.008506

C 2.916681 -

0.248902 -

0.106401

C 1.726257 0.496303 0.114883

C 1.088200 0.435300 1.320891

N 1.558263 -

0.313966 2.356867

H 1.250611 1.091440 -

0.659400

H 0.154702 0.948526 1.501352

C 0.801559 -

0.379292 3.635030

H 0.085668 0.435773 3.605405

141 | P a g e

H 1.514929 -

0.200904 4.443639

TS1

C 0.061867 -

1.707982 3.859823

H 0.780783 -

2.480171 4.158203

H -

0.582819 -

1.542598 4.729230

C -

0.770681 -

2.255217 2.691786

H -

0.111929 -

2.578369 1.876052

H -

1.290334 -

3.160962 3.013053

H 3.050277 -

1.579456 3.043097

H 4.312577 -

1.574948 0.951722

Br -

0.655834 1.735319

-2.297717

C -

1.801838 -

1.312029 2.052437

O -

1.727921 -

0.087940 2.239447

O -

2.643296 -

1.911034 1.295031

H -

3.346846 -

1.178107 0.475511

N 3.550169 -

0.250554 -

1.295824

C 4.824295 -

0.948745 -

1.452246

H 5.153387 -

0.848773 -

2.483728

H 5.600120 -

0.527189 -

0.803322

H 4.720507 -

2.015196 -

1.232108

C 3.078713 0.578142 -

2.415756

H 3.448080 1.605676 -

2.329055

H 3.450008 0.147322 -

3.344428

H 1.989664 0.605352 -

2.466226

C -

2.953194 -

0.663197 -

1.510847

H -

2.164952 -

1.402213 -

1.372486

C -

2.715049 0.623900

-0.881511

H -

3.331880 1.466811

-1.149807

1.77 Å

142 | P a g e

H -

2.056718 0.708102

-0.034691

O -

3.858719 -

0.631937 -

0.373485

C -

3.638837 -

0.746330 -

2.847249

H -

2.917452 -

0.521337 -

3.636131

H -

4.042805 -

1.749170 -

3.006067

H -

4.457204 -

0.025477 -

2.906485

143 | P a g e

C -

3.453871 -

1.376485 -

0.302415

B

C -

3.914550 -

0.175100 0.166678

C -

3.059308 0.964465 0.176818

C -

1.749384 0.766046

-0.330419

C -

1.354069 -

0.464794 -

0.784862

N -

2.195227 -

1.531482 -

0.774632

H -

1.013539 1.556409

-0.361294

H -

0.343165 -

0.681242 -

1.117581

C -

1.711123 -

2.865227 -

1.235550

H -

0.862999 -

2.674660 -

1.886389

H -

2.525973 -

3.315000 -

1.807922

C -

1.276772 -

3.785592 -

0.086579

H -

2.165849 -

4.137398 0.452574

H -

0.842023 -

4.668893 -

0.566925

C -

0.279326 -

3.204675 0.927379

H -

0.757667 -

2.397567 1.498586

H -

0.032841 -

3.973458 1.662553

H -

4.080725 -

2.258386 -

0.317904

H -

4.931792 -

0.124684 0.524373

Br 1.923407 2.068754 -

0.915841

C 1.049805 -

2.618011 0.380262

O 1.034276 -

2.138668 -

0.788770

O 2.004990 -

2.618645 1.186535

H 3.434741 -

1.651803 0.979749

N -

3.470215 2.164531 0.644436

C -

4.823406 2.333649 1.170095

H -

4.949563 3.363007 1.496358

144 | P a g e

H -

5.578170 2.125266 0.405110

H -

5.002422 1.680527 2.030117

C -

2.551659 3.306473 0.644832

H -

2.235022 3.560404

-0.370785

H -

3.061163 4.167819 1.069868

H -

1.662532 3.100029 1.246779

C 3.527156 0.300528 0.855834

H 2.635298 0.340263 1.496719

C 3.084647 0.440513 -

0.602932

H 3.928315 0.580058 -

1.275918

H 2.462646 -

0.399090 -

0.907443

O 4.148380 -

0.965898 0.953874

C 4.524826 1.361649 1.298848

H 4.108014 2.367069 1.203901

H 4.804893 1.191626 2.340637

H 5.431421 1.297046 0.689637

145 | P a g e

C 3.556574 1.956731 -0.740973

C

C 4.337966 0.834433 -0.731459

C 3.738374 -0.456011 -0.647366

C 2.320230 -0.483606 -0.593516

C 1.601150 0.682282 -0.614614

N 2.204501 1.897670 -0.687941

H 1.763520 -1.404411 -0.501153

H 0.521435 0.676052 -0.553835

C 1.402447 3.154412 -0.635630

H 0.382753 2.888184 -0.904783

H 1.812833 3.827121 -1.391946

C 1.391519 3.809818 0.752821

H 2.362121 4.278316 0.957269

H 0.656123 4.615863 0.684534

C 1.019575 2.855361 1.898422

H 1.866195 2.221897 2.176986

H 0.772021 3.446426 2.785901

H 3.986341 2.948266 -0.792568

H 5.408835 0.960248 -0.780650

Br 4.814366 0.173082 -1.285966

C 0.188980 1.940509 1.574240

O 1.069994 2.409644 0.819804

O 0.139223 0.773669 2.056249

H 0.935389 -0.401310 1.161035

N 4.480434 -1.584197 -0.620332

C 5.938556 -1.515051 -0.688448

H 6.352480 -0.960076 0.159446

H 6.341199 -2.524409 -0.659320

H 6.273889 -1.042593 -1.617402

C 3.828113 -2.894472 -0.530361

H 3.196882 -3.082497 -1.403720

H 4.594308 -3.664868 -0.487734

H 3.208528 -2.969175 0.364837

C 2.675632 -0.991667 0.374305

H 3.010929 -1.941798 -0.053527

C 2.924092 0.120433 -0.647650

H 2.704441 1.104081 -0.236425

H 2.341345 -0.059321 -1.548147

O 1.257408 -1.104179 0.528144

C 3.371815 -0.760569 1.712634

H 4.455280 -0.709477 1.584345

H 3.141115 -1.581666 2.395084

H 3.026100 0.173364 2.162522

C 0.389430 -3.656972 0.932226

O 0.685892 -3.406609 0.560556

O 1.429759 -4.000547 1.307521

146 | P a g e

C -

0.433256 0.183308 0.531999

TS2

C -

0.700601 1.311320 1.255354

C -

0.115650 2.559590 0.887116

C 0.694556 2.542086 -

0.281213

C 0.935784 1.371976 -

0.942352

N 0.384796 0.192991 -

0.549452

H 1.199709 3.430524 -

0.626793

H 1.618468 1.315231 -

1.776321

C 0.716632 -

1.063416 -

1.272985

H 1.367987 -

0.767829 -

2.088510

H -

0.215064 -

1.461980 -

1.684308

C 1.425711 -

2.128237 -

0.414899

H 0.681285 -

2.719766 0.130133

H 1.888742 -

2.814492 -

1.130691

C 2.473973 -

1.629083 0.588856

H 1.991847 -

1.167997 1.457524

H 3.021664 -

2.484890 0.993314

H -

0.854157 -

0.776118 0.801277

H -

1.341924 1.220991 2.118449

Br 6.810359 3.351181 -

2.457945

C 3.502201 -

0.603390 0.089249

O 3.439337 -

0.163231 -

1.069075

O 4.339407 -

0.252872 0.991754

H 4.703873 0.967908 0.993520

N -

0.313924 3.680878 1.600838

C -

1.001631 3.619743 2.890386

H -

0.465597 2.972039 3.591059

147 | P a g e

H -

1.044101 4.620143 3.313379

H -

2.027726 3.258508 2.776032

C 0.357270 4.931119 1.219937

H 0.090344 5.210988 0.197620

H 0.016001 5.723039 1.882422

H 1.444501 4.843167 1.300054

C 6.018847 2.564179 0.255824

H 6.170495 3.611619 0.524703

C 5.533794 2.495667 -

1.193182

H 5.393985 1.474627 -

1.539172

H 4.615800 3.063583 -

1.308488

O 4.959120 2.079801 1.096171

C 7.279430 1.754521 0.539763

H 8.116557 2.126820 -

0.053661

H 7.536453 1.834485 1.597894

H 7.123879 0.699023 0.301973

C 3.599922 3.112838 1.488426

O 3.793477 4.195875 1.006370

O 2.841165 2.440811 2.125742

C 3.920704 0.908221 -0.635684

D

C 4.150917 -0.394807 -0.294909

C 3.138778 -1.382943 -0.494151

C 1.961218 -0.938533 -1.159136

C 1.800175 0.376710 -1.470790

N 2.753411 1.313748 -1.195132

H 1.132344 -1.606467 -1.340031

H 0.882031 0.751981 -1.896588

C 2.482115 2.749352 -1.446979

H 1.525140 2.787416 -1.957853

H 3.253589 3.124926 -2.124613

C 2.426773 3.622465 -0.177074

H 3.442608 3.903451 0.120190

H 1.932910 4.552206 -0.475852

C 1.729889 3.027163 1.052406

H 2.319260 2.210766 1.483533

H 1.667639 3.780762 1.842754

H 4.658865 1.679339 -0.458394

H 5.094903 -0.637321 0.168671

Br 4.738985 -0.376885 -1.126189

C 0.344578 2.445811 0.835030

O 0.176047 2.335128 -0.260692

O 0.189419 2.035124 1.972548

H 0.807710 1.264731 1.808443

N 3.284583 -2.649286 -0.079832

C 4.515618 -3.077214 0.579976

H 4.480531 -4.154763 0.720981

148 | P a g e

H 5.393973 -2.847275 -0.029702

H 4.626585 -2.603530 1.561437

C 2.178194 -3.614164 -0.190046

H 2.122773 -4.027234 -1.203448

H 2.364736 -4.429066 0.506815

H 1.225016 -3.149192 0.074062

C 2.798486 -0.538649 1.072334

H 2.926730 -1.621044 1.025025

C 2.961097 0.038012 -0.332906

H 2.874534 1.122047 -0.346931

H 2.243852 -0.417232 -1.007569

O 1.445069 -0.266269 1.487449

C 3.720915 0.075430 2.115682

H 4.765910 -0.120540 1.869199

H 3.505913 -0.353424 3.096450

H 3.578713 1.158880 2.174777

C 0.378188 -1.173122 1.040920

O 0.727887 -2.079173 0.271132

O 0.718088 -0.846319 1.499810

149 | P a g e

C 0.531328 0.781110 0.075689

TS3

C 0.100118 1.832824 0.835866

C 0.733679 3.109434 0.730774

C 1.782383 3.204723 -

0.226860

C 2.161697 2.108940 -

0.947747

N 1.556394 0.896812 -

0.804920

H 2.332843 4.122023 -

0.407460

H 2.979220 2.152688 -

1.653757

C 2.028229 -0.276555 -

1.585315

H 2.701692 0.112821 -

2.342770

H 1.158313 -0.714900 -

2.079789

C 2.755320 -1.337510 -

0.741808

H 2.024108 -1.939716 -

0.192237

H 3.230608 -2.013651 -

1.458625

C 3.793536 -0.820605 0.259858

H 3.312612 -0.303771 1.097153

H 4.316335 -1.665912 0.716161

H 0.069089 -0.194833 0.144366

H 0.724355 1.663361 1.511597

Br 4.304292 5.784168 -

0.859201

C 4.844152 0.128889 -

0.299474

O 4.869883 0.495695 -

1.461004

O 5.673685 0.514998 0.646821

H 6.295019 1.246055 0.368272

N 0.359075 4.153292 1.492144

C 0.777607 4.033641 2.405624

H 0.902835 4.976241 2.932404

H 1.706297 3.816807 1.867363

H 0.605081 3.250321 3.149030

C 0.975587 5.478889 1.336385

H 0.511864 6.036635 0.516240

H 0.841613 6.034598 2.262687

H 2.043620 5.403160 1.138650

C 6.968586 3.957563 -

0.346638

H 7.930941 4.478391 -

0.395015

C 6.058023 4.833554 0.505365

H 5.306196 4.363603 1.113324

H 6.356347 5.831067 0.770106

150 | P a g e

O 7.174421 2.734140 0.380156

C 6.548127 3.590080 -

1.761427

H 6.453760 4.485212 -

2.374932

H 7.314884 2.939180 -

2.187704

H 5.598720 3.056317 -

1.775021

C 7.543168 2.995242 1.776244

O 7.361429 4.206211 2.077428

O 7.928431 2.026920 2.392815

151 | P a g e

C 3.792659 1.486510 -0.150250

E

C 4.164214 0.279228 0.374444

C 3.290355 -0.851250 0.287494

C 2.061601 -0.634170 -0.399610

C 1.762353 0.597307 -0.898480

N 2.604570 1.666964 -0.778320

H 1.303609 -1.408890 -0.545480

H 0.826304 0.777509 -1.410520

C 2.200764 3.001357 -1.280000

H 1.384467 2.839207 -1.979310

H 3.046260 3.420394 -1.829950

C 1.757247 3.969792 -0.171810

H 2.631909 4.306688 0.394508

H 1.356333 4.853110 -0.677460

C 0.728652 3.424079 0.822286

H 1.139868 2.596156 1.408590

H 0.478207 4.195279 1.556817

H 4.437187 2.353743 -0.088690

H 5.130280 0.213933 0.851949

Br 0.652219 -2.734780 -0.865700

C 0.571767 2.935845 0.208779

O 0.822013 2.958029 -0.978780

O 1.386306 2.461724 1.145492

H 2.180162 2.037198 0.752069

N 3.621781 -2.037460 0.824121

C 4.911325 -2.214690 1.489605

H 4.973499 -3.237510 1.854111

H 5.745365 -2.046590 0.800532

H 5.014692 -1.540790 2.345675

C 2.765990 -3.232820 0.753517

H 3.244409 -3.990380 0.125798

H 2.639706 -3.635490 1.761228

H 1.777856 -3.020990 0.345991

C 3.996320 0.058081 -0.787460

H 4.960954 0.506735 -1.048110

C 4.181607 -1.342930 -0.204720

H 3.269011 -1.941970 -0.276560

H 5.034895 -1.878590 -0.616880

O 3.530038 0.786356 0.397138

C 3.010320 0.176098 -1.926140

H 3.430863 -0.309640 -2.811780

H 2.822224 1.224531 -2.165570

H 2.074674 -0.331500 -1.682030

C 3.947413 0.123470 1.524145

O 4.455470 -1.073610 1.195284

O 3.866219 0.576627 2.623750

152 | P a g e

C -8.511981 -

0.453947 0.340229

C -9.639057 0.158980 -0.163410

C -

10.113374 -

0.151590 -1.453109

C -9.336851 -

1.084072 -2.205695

C -8.204012 -

1.622617 -1.665090

N -7.764283 -

1.295156 -0.425897

H -9.628319 -

1.399758 -3.195441

H -7.605935 -

2.342931 -2.206381

C -6.612734 -

1.994012 0.194365

H -6.288222 -

2.757778 -0.514888

H -7.019623 -

2.487888 1.085168

C -5.458873 -

1.060856 0.558219

H -5.791049 -

0.316993 1.286819

H -4.708780 -

1.660813 1.080026

C -4.822950 -

0.368186 -0.646654

H -4.443329 -

1.099213 -1.370464

H -5.549829 0.239463 -1.195895

H -8.144909 -

0.244271 1.330042

H -

10.181292 0.815001 0.498992

Br -9.337071 -

2.412184 2.439486

C -3.666599 0.536030 -0.279799

O -3.217559 0.673535 0.836378

O -3.183232 1.180635 -1.354830

H -2.438503 1.749857 -1.076648

N -

11.250466 0.394123 -1.956391

C -

12.082180 1.251388 -1.113003

H -

12.432370 0.718574 -0.223276

H -

11.533230 2.142848 -0.794795

H -

12.949465 1.575097 -1.684013

C -

11.739295 0.007300 -3.276574

153 | P a g e

H -

10.983261 0.188036 -4.045934

H -

12.032119 -

1.048234 -3.310301

H -

12.611433 0.609879 -3.520525

C -0.935544 2.956535 1.156327

C 0.574825 2.978096 1.392828

C 0.126613 3.204258 -0.868869

H -1.456308 2.114653 1.605945

H -1.412713 3.897617 1.441269

H 0.978292 1.974065 1.535245

C 1.051562 3.909107 2.482747

H 0.631330 3.588821 3.440539

H 2.137861 3.871396 2.563655

H 0.732927 4.935945 2.287743

O 1.065285 3.430246 0.083962

O -1.041147 2.822456 -0.285115

O 0.296131 3.318041 -2.040182

C 7.959520 -

1.134208 0.035742

C 8.306178 -

1.955771 -1.014799

C 9.112273 -

1.478290 -2.067068

C 9.492384 -

0.103542 -1.999809

C 9.075804 0.670063 -0.954010

N 8.288696 0.186753 0.037500

H 10.124364 0.349230 -2.748006

H 9.361740 1.709607 -0.869760

C 7.962316 1.000427 1.232885

H 8.516266 1.936465 1.139506

H 8.367231 0.437577 2.082752

C 6.466230 1.263638 1.398925

H 5.925707 0.319209 1.500201

H 6.332011 1.778286 2.354196

C 5.859384 2.096500 0.270517

H 6.362771 3.065419 0.173808

H 5.978409 1.605142 -0.701438

H 7.363566 -

1.485850 0.860335

H 8.011188 -

2.990985 -0.948894

Br 9.544305 -

1.941510 2.438407

C 4.382678 2.372608 0.450725

O 3.703286 1.965892 1.366820

O 3.899189 3.138143 -0.541783

H 2.943100 3.280094 -0.394039

N 9.518669 -

2.277549 -3.086941

C 9.203023 -

3.704892 -3.064167

154 | P a g e

H 9.644856 -

4.199853 -2.193302

H 8.121353 -

3.867371 -3.048698

H 9.600622 -

4.169498 -3.963700

C 10.411876 -

1.763815 -4.121379

H 9.974295 -

0.898320 -4.627215

H 11.387157 -

1.477526 -3.711862

H 10.571220 -

2.539267 -4.867350

C 4.506058 -3.219033 -1.566193

C 5.343730 -2.363416 -2.241861

C 5.861189 -1.182477 -1.622969

C 5.393530 -0.914745 -0.295968

C 4.573122 -1.818891 0.336783

N 4.144364 -2.975877 -0.268548

H 5.625685 -0.002284 0.254167

H 4.220190 -1.620784 1.340075

C 3.328228 -4.026964 0.434711

H 4.029469 -4.739104 0.886867

H 2.794454 -4.563373 -0.361554

C 2.361368 -3.474088 1.487089

H 2.041522 -2.466343 1.196994

H 1.461289 -4.096824 1.486306

C 2.935533 -3.459175 2.937923

H 2.765941 -4.426513 3.416754

H 4.013368 -3.268791 2.921433

H 4.033274 -4.084886 -2.033415

H 5.591379 -2.620030 -3.261333

Br 2.238476 -5.676048 -2.457503

C 2.286084 -2.372761 3.755588

O 1.351875 -2.544928 4.569495

O 2.791261 -1.166232 3.457187

H 2.305209 -0.365070 3.833507

N 6.730283 -0.376631 -2.292963

C 7.190253 -0.760079 -3.637610

H 7.714001 -1.724373 -3.627297

H 6.354608 -0.825296 -4.344251

H 7.882171 0.001227 -3.996826

C 7.415885 0.789564 -1.699784

H 6.932510 1.181686 -0.801264

H 8.449579 0.526394 -1.439374

H 7.438718 1.594765 -2.441379

C 3.647037 3.927709 -0.158921

C 3.097383 3.954896 -1.421121

C 1.911881 4.700689 -1.696119

C 1.354800 5.433720 -0.602934

C 1.964626 5.396865 0.624355

155 | P a g e

N 3.092608 4.651685 0.860956

H 0.406282 5.953860 -0.680250

H 1.560538 5.944240 1.465078

C 3.658795 4.535198 2.242871

H 3.429246 5.471071 2.761316

H 4.740946 4.422415 2.143044

C 3.113174 3.305108 2.988460

H 3.447988 2.413700 2.445807

H 3.623428 3.253529 3.957220

C 1.589824 3.339798 3.185956

H 1.320811 4.017998 4.009889

H 1.066357 3.719815 2.303869

H 4.511722 3.314534 0.115577

H 3.582706 3.366781 -2.186627

Br 6.137690 2.126657 1.328024

C 0.975859 1.994971 3.483333

O 1.591182 1.045267 4.009232

O 0.310932 1.948004 3.118982

H 0.831134 1.080868 3.220601

N 1.341988 4.713091 -2.931171

C 2.003052 4.031990 -4.051057

H 3.021764 4.408690 -4.206762

H 2.056768 2.947861 -3.887057

H 1.431121 4.213760 -4.960344

C 0.102920 5.475870 -3.198165

H 0.642537 5.335817 -2.404810

H 0.312153 6.549629 -3.291724

H 0.323891 5.121309 -4.137927

C 2.999930 -2.527497 -1.139850

C 2.092085 -1.908530 -1.967843

C 0.911462 -2.577789 -2.416936

C 0.737185 -3.922758 -1.959518

C 1.688122 -4.492840 -1.151129

N 2.808163 -3.818693 -0.730143

H 0.145650 -4.525277 -2.176793

H 1.584183 -5.514221 -0.809220

C 3.782229 -4.448827 0.218281

H 3.777677 -5.523948 0.015603

H 4.766540 -4.027888 -0.007044

C 3.464104 -4.129414 1.690006

H 3.529411 -3.044753 1.817210

H 4.282808 -4.536286 2.295198

C 2.113881 -4.677865 2.173604

H 2.174289 -5.754093 2.389955

H 1.341438 -4.577308 1.402678

H 3.912166 -2.044982 -0.777212

H 2.309346 -0.892617 -2.263151

Br 5.966739 -1.643432 0.303463

C 1.555936 -3.992581 3.399563

O 2.173347 -3.197525 4.132633

O 0.270479 -4.331486 3.618138

H 0.236788 -3.727483 4.253742

N 0.020927 -1.949266 -3.231831

C 0.281561 -0.570687 -3.672395

156 | P a g e

H 1.182976 -0.505713 -4.296353

H 0.397776 0.105499 -2.818045

H 0.568455 -0.231516 -4.264359

C 1.148617 -2.606944 -3.848631

H 1.445776 -3.538484 -3.357660

H 0.942692 -2.830068 -4.904022

H 2.001822 -1.922493 -3.795302

C 4.414243 3.040106 -0.996106

C 4.913324 2.440992 -2.133696

C 5.975921 1.494154 -2.052844

C 6.585006 1.332439 -0.773912

C 6.074444 1.980131 0.316942

N 4.966195 2.778780 0.228187

H 7.411913 0.658215 -0.625332

H 6.495136 1.843273 1.302324

C 4.278721 3.233388 1.474979

H 5.054900 3.535662 2.185611

H 3.673787 4.106720 1.205207

C 3.369768 2.136814 2.059326

H 2.619108 1.868107 1.307023

H 2.807056 2.599172 2.878567

C 4.089117 0.873821 2.564215

H 4.854618 1.118906 3.313491

H 4.623284 0.317561 1.771648

H 3.585282 3.753363 -1.003610

H 4.440994 2.678226 -3.076562

Br 2.147654 5.594193 -0.370699

C 3.158023 -0.134457 3.186860

O 1.904716 -0.067307 3.189636

O 3.804582 -1.178515 3.720652

H 3.198389 -1.932754 4.002119

N 6.392366 0.761824 -3.122148

C 5.879358 1.040780 -4.466995

H 5.935000 2.110743 -4.693050

H 4.837086 0.711990 -4.588044

H 6.494133 0.511185 -5.195302

C 7.261341 -0.419024 -2.919337

H 6.926233 -0.977438 -2.035101

H 8.313492 -0.130903 -2.799002

H 7.178253 -1.066209 -3.794211

157 | P a g e

The Cartesian coordinates for Chapter 3

C 0.952 -1.92 -2.215

O 1.694 -1.65 0.033

H 1.892 -1.489 -2.564

H 0.537 -2.59 -2.967

Br -0.325 -0.374 -2.158

C 1.111 -2.564 -0.845

H 0.112 -2.861 -0.485

C 1.975 -3.829 -0.992

H 1.511 -4.577 -1.645

H 2.961 -3.574 -1.394

H 2.113 -4.271 -0.002

C -2.67 1.472 -0.126

C -2.846 0.021 0.256

H -1.61 1.711 -0.135

H -3.012 1.604 -1.157

N -3.96 -0.601 -0.16

C -4.126 -2.067 -0.096

H -4.496 -2.396 -1.074

H -4.888 -2.305 0.654

C -2.804 -2.736 0.239

H -2.972 -3.786 0.494

H -2.13 -2.701 -0.624

C -2.161 -2.003 1.409

H -2.82 -2.023 2.287

H -1.186 -2.403 1.696

N -1.948 -0.587 1.029

C -0.703 0.118 1.426

H -0.989 1.123 1.742

H -0.064 0.168 0.544

C 0.122 -0.535 2.565

C 1.259 0.479 2.962

H 0.887 1.498 3.104

H 1.654 0.15 3.924

N 2.414 0.464 2.031

C 3.446 -0.538 2.394

H 3.631 -0.424 3.465

H 3.025 -1.531 2.227

C 4.724 -0.307 1.606

H 5.417 -1.134 1.784

H 5.216 0.615 1.937

158 | P a g e

C 4.395 -0.216 0.126

H 5.273 0.094 -0.447

H 4.019 -1.171 -0.255

N 3.351 0.8 -0.088

C 2.442 1.087 0.847

C 1.505 2.243 0.565

H 0.854 1.978 -0.275

H 0.858 2.39 1.424

C 2.239 3.575 0.266

H 3.111 3.669 0.925

H 1.558 4.389 0.537

C 2.654 3.754 -1.201

H 3.067 4.76 -1.335

H 1.753 3.703 -1.827

C 3.666 2.718 -1.703

H 4.637 2.86 -1.212

H 3.83 2.865 -2.776

C 3.207 1.273 -1.483

H 2.171 1.126 -1.803

H 3.814 0.593 -2.084

C -5.141 0.162 -0.622

H -5.907 -0.588 -0.826

H -4.925 0.653 -1.58

C -5.677 1.167 0.413

H -6.728 1.359 0.167

H -5.67 0.687 1.4

C -4.938 2.513 0.461

H -5.036 3 -0.519

H -5.44 3.169 1.181

C -3.448 2.422 0.815

H -3.321 2.089 1.854

H -3.002 3.42 0.748

H -0.529 -0.564 3.467

O 0.621 -1.763 2.248

H 1.24 -1.74 1.013

159 | P a g e

C 0.288 -0.747 -2.915

O 1.26 -1.587 -0.901

H 1.292 -0.619 -3.32

H -0.433 -0.911 -3.715

Br -0.206 1.038 -2.155

C 0.244 -1.817 -1.837

H -0.741 -1.751 -1.347

C 0.365 -3.202 -2.491

H -0.457 -3.403 -3.188

H 1.314 -3.291 -3.031

H 0.352 -3.962 -1.705

C -2.491 1.556 0.387

C -2.819 0.081 0.378

H -1.421 1.686 0.51

H -2.735 1.984 -0.588

N -4.004 -0.288 -0.136

C -4.445 -1.695 -0.203

H -4.942 -1.837 -1.168

H -5.192 -1.865 0.583

C -3.267 -2.64 -0.053

H -3.627 -3.66 0.104

H -2.663 -2.641 -0.966

C -2.407 -2.209 1.124

H -2.963 -2.292 2.067

H -1.49 -2.801 1.179

N -1.993 -0.793 0.954

C -0.664 -0.351 1.47

H -0.832 0.456 2.191

H -0.092 0.02 0.617

C 0.165 -1.481 2.137

C 1.46 -0.86 2.775

H 1.272 0.081 3.298

H 1.817 -1.569 3.522

N 2.57 -0.719 1.804

C 3.39 -1.95 1.679

H 3.626 -2.273 2.697

H 2.764 -2.718 1.219

C 4.664 -1.682 0.897

H 5.165 -2.63 0.683

H 5.354 -1.065 1.484

C 4.311 -0.972 -0.398

H 5.215 -0.659 -0.927

H 3.706 -1.609 -1.052

160 | P a g e

N 3.529 0.239 -0.101

C 2.695 0.295 0.94

C 1.973 1.601 1.184

H 1.326 1.813 0.327

H 1.32 1.495 2.044

C 2.938 2.79 1.437

H 3.774 2.451 2.061

H 2.392 3.532 2.03

C 3.459 3.469 0.164

H 4.061 4.34 0.445

H 2.6 3.855 -0.402

C 4.282 2.556 -0.754

H 5.23 2.281 -0.276

H 4.536 3.105 -1.668

C 3.536 1.279 -1.154

H 2.507 1.495 -1.454

H 4.015 0.816 -2.019

C -5.041 0.707 -0.502

H -5.854 0.129 -0.945

H -4.663 1.364 -1.293

C -5.577 1.518 0.688

H -6.561 1.909 0.407

H -5.741 0.835 1.532

C -4.684 2.693 1.11

H -4.632 3.409 0.278

H -5.159 3.224 1.943

C -3.255 2.305 1.508

H -3.262 1.693 2.419

H -2.695 3.214 1.749

H -0.418 -1.825 3.021

O 0.459 -2.497 1.275

H 0.953 -2.008 0.016

161 | P a g e

C 1.094 -2.525 -1.953

O 1.585 -1.971 0.011

H 1.859 -1.991 -2.504

H 0.162 -2.715 -2.467

Br -0.353 -0.191 -2.101

C 1.481 -3.18 -0.694

H 0.67 -3.828 -0.311

C 2.771 -3.998 -0.749

H 2.646 -4.925 -1.321

H 3.582 -3.415 -1.198

H 3.059 -4.261 0.276

C -2.76 1.548 -0.061

C -2.898 0.069 0.207

H -1.706 1.81 -0.077

H -3.096 1.723 -1.087

N -4.037 -0.524 -0.171

C -4.199 -1.978 -0.012

H -4.951 -2.311 -0.729

H -4.566 -2.202 0.999

C -2.855 -2.638 -0.274

H -2.93 -3.722 -0.155

H -2.546 -2.421 -1.302

C -1.826 -2.092 0.7

H -1.906 -2.543 1.69

H -0.821 -2.274 0.324

N -1.935 -0.615 0.839

C -0.697 0.066 1.262

H -0.953 1.097 1.492

H -0.02 0.035 0.405

C 0.027 -0.482 2.501

C 1.202 0.485 2.847

H 0.849 1.511 2.972

H 1.605 0.168 3.81

N 2.328 0.421 1.889

C 3.355 -0.594 2.232

H 3.54 -0.509 3.305

H 2.95 -1.586 2.026

C 4.627 -0.351 1.44

H 5.329 -1.171 1.615

H 5.111 0.579 1.762

162 | P a g e

C 4.274 -0.273 -0.034

H 5.141 0.021 -0.631

H 3.88 -1.228 -0.394

N 3.232 0.745 -0.243

C 2.35 1.057 0.703

C 1.445 2.243 0.441

H 0.794 2.011 -0.41

H 0.797 2.392 1.299

C 2.225 3.559 0.19

H 3.083 3.613 0.873

H 1.56 4.385 0.466

C 2.68 3.765 -1.261

H 3.137 4.756 -1.353

H 1.792 3.77 -1.908

C 3.659 2.703 -1.775

H 4.623 2.784 -1.257

H 3.856 2.882 -2.838

C 3.126 1.276 -1.625

H 2.087 1.183 -1.957

H 3.706 0.587 -2.242

C -5.204 0.251 -0.653

H -5.956 -0.492 -0.92

H -4.942 0.777 -1.578

C -5.789 1.218 0.391

H -6.825 1.427 0.097

H -5.837 0.702 1.358

C -5.044 2.553 0.526

H -5.102 3.085 -0.434

H -5.564 3.181 1.258

C -3.566 2.429 0.921

H -3.472 2.03 1.939

H -3.118 3.429 0.934

H -0.652 -0.454 3.365

O 0.492 -1.798 2.374

H 0.913 -1.912 1.463

163 | P a g e

C -1.973 3.332 -2.223

O -2.722 3.031 -1.02

H -2.483 4.001 -2.915

H -1.459 2.476 -2.658

Br -0.018 0.365 -1.128

C -1.532 3.849 -0.921

H -0.701 3.327 -0.444

C -1.739 5.282 -0.505

H -0.851 5.878 -0.744

H -2.6 5.716 -1.022

H -1.913 5.349 0.574

C 2.608 -1.678 -0.24

C 2.787 -0.275 0.293

H 1.789 -2.157 0.286

H 2.303 -1.628 -1.287

N 3.605 0.547 -0.362

C 3.807 1.968 0

H 3.62 2.561 -0.9

H 4.862 2.091 0.272

C 2.888 2.403 1.129

H 3.271 3.32 1.585

H 1.882 2.595 0.754

C 2.816 1.276 2.151

H 3.811 1.04 2.552

H 2.171 1.543 2.983

N 2.283 0.067 1.495

C 1.081 -0.593 2.038

H 1.357 -1.311 2.821

H 0.617 -1.118 1.213

C 0.02 0.39 2.595

C -1.361 -0.315 2.783

H -1.235 -1.322 3.185

H -1.918 0.248 3.534

N -2.21 -0.323 1.578

C -2.966 0.937 1.348

H -3.208 1.354 2.327

H -2.326 1.641 0.817

C -4.212 0.668 0.528

H -4.699 1.618 0.297

H -4.918 0.034 1.078

C -3.779 -0.001 -0.761

H -4.641 -0.347 -1.337

H -3.186 0.691 -1.369

164 | P a g e

N -2.944 -1.181 -0.469

C -2.212 -1.284 0.639

C -1.438 -2.567 0.831

H -0.686 -2.609 0.034

H -0.892 -2.53 1.768

C -2.311 -3.847 0.826

H -3.248 -3.652 1.363

H -1.777 -4.61 1.403

C -2.603 -4.406 -0.573

H -3.149 -5.35 -0.475

H -1.646 -4.65 -1.055

C -3.384 -3.452 -1.483

H -4.408 -3.319 -1.111

H -3.467 -3.897 -2.481

C -2.727 -2.077 -1.629

H -1.652 -2.147 -1.821

H -3.149 -1.548 -2.485

C 4.31 0.13 -1.598

H 4.748 1.041 -2.006

H 3.571 -0.216 -2.328

C 5.416 -0.908 -1.364

H 6.094 -0.868 -2.224

H 6.004 -0.604 -0.488

C 4.908 -2.345 -1.2

H 4.442 -2.664 -2.142

H 5.761 -3.013 -1.035

C 3.891 -2.533 -0.067

H 4.353 -2.317 0.905

H 3.587 -3.584 -0.038

H 0.32 0.713 3.6

O -0.09 1.554 1.816

H -0.13 1.281 0.862

165 | P a g e

C 3.545 -0.519 -0.445

O 1.191 -1.16 -0.206

H 3.837 -0.925 0.52

H 4.386 -0.526 -1.14

Br 3.17 1.405 -0.11

C 2.324 -1.237 -1.026

H 2.086 -0.749 -1.989

C 2.708 -2.7 -1.305

H 3.557 -2.778 -1.994

H 2.959 -3.204 -0.367

H 1.849 -3.211 -1.751

C -1.766 0.138 -0.004

N -2.805 0.919 0.362

C -2.665 2.383 0.427

C -1.557 2.863 -0.505

C -0.29 2.052 -0.257

N -0.592 0.626 -0.328

H -3.624 2.826 0.14

H -1.876 2.734 -1.547

H 0.479 2.269 -0.999

C -1.957 -1.356 -0.097

H -2.216 -1.743 0.894

H -0.983 -1.781 -0.341

C -3.01 -1.777 -1.146

H -2.798 -2.815 -1.427

H -2.877 -1.179 -2.057

C -4.466 -1.693 -0.665

H -5.129 -2.08 -1.448

H -4.586 -2.361 0.2

C -4.933 -0.288 -0.263

H -4.938 0.38 -1.135

H -5.967 -0.346 0.098

C -4.079 0.354 0.84

H -4.623 1.183 1.298

H -3.883 -0.368 1.642

H 0.141 2.276 0.727

H -1.373 3.929 -0.343

H -2.457 2.679 1.465

H 0.259 -0.105 -0.36

C 1.274 -1.511 1.69

166 | P a g e

O 2.328 -2.029 1.908

O 0.21 -1.103 2.055

C 3.24 0.181 -0.796

O 2.239 1.163 0.769

H 3.121 0.978 -1.519

H 3.314 -0.831 -1.168

Br 0.811 -0.942 -1.666

C 3.491 0.567 0.6

H 3.634 -0.322 1.242

C 4.658 1.533 0.815

H 5.629 1.055 0.633

H 4.551 2.4 0.155

H 4.625 1.886 1.851

C -0.853 0.207 0.65

N -1.888 -0.603 0.373

C -1.834 -2.02 0.768

C -1.034 -2.2 2.055

C 0.319 -1.517 1.9

N 0.131 -0.139 1.461

H -2.862 -2.37 0.904

H -1.581 -1.76 2.898

H 0.87 -1.5 2.846

C -0.82 1.604 0.084

H -0.724 1.512 -1.004

H 0.106 2.066 0.426

C -2.033 2.483 0.454

H -1.727 3.53 0.349

H -2.286 2.341 1.513

C -3.268 2.245 -0.425

H -4.055 2.959 -0.15

H -2.998 2.468 -1.467

C -3.837 0.822 -0.363

H -4.24 0.617 0.638

H -4.677 0.746 -1.065

C -2.828 -0.278 -0.717

H -3.363 -1.204 -0.935

H -2.254 -0.031 -1.619

H 0.928 -2.035 1.147

H -0.905 -3.267 2.259

167 | P a g e

H -1.374 -2.584 -0.054

H 1.045 0.417 1.293

C 2.856 1.765 -0.274

O 2.57 1.247 1.056

H 3.447 2.68 -0.268

H 2.022 1.711 -0.971

Br 0.646 -0.807 -1.805

C 3.463 0.506 0.166

H 2.997 -0.396 -0.233

C 4.894 0.404 0.617

H 5.527 0.1 -0.225

H 5.254 1.364 1.001

H 4.999 -0.347 1.407

C -0.806 0.133 0.668

N -1.832 -0.678 0.392

C -1.698 -2.127 0.634

C -0.816 -2.412 1.846

C 0.497 -1.651 1.707

N 0.204 -0.244 1.45

H -2.703 -2.531 0.787

H -1.33 -2.109 2.766

H 1.098 -1.713 2.619

C -0.835 1.576 0.24

H -0.764 1.584 -0.853

H 0.082 2.038 0.612

C -2.059 2.383 0.723

H -1.785 3.443 0.699

H -2.274 2.141 1.772

C -3.312 2.18 -0.139

H -4.107 2.847 0.215

H -3.078 2.492 -1.167

C -3.841 0.741 -0.174

H -4.212 0.448 0.818

H -4.698 0.697 -0.857

C -2.818 -0.301 -0.642

H -3.336 -1.225 -0.906

H -2.274 0.015 -1.541

H 1.079 -2.035 0.859

H -0.624 -3.488 1.906

168 | P a g e

H -1.263 -2.565 -0.275

H 1.017 0.383 1.428

C 2.978 1.272 -0.344

O 2.488 1.472 1.02

H 3.304 2.198 -0.82

H 2.379 0.584 -0.944

Br 0.511 -1.114 -1.707

C 3.741 0.77 0.807

H 3.666 -0.302 1.006

C 4.973 1.458 1.34

H 5.871 1.015 0.888

H 4.949 2.519 1.096

H 5.042 1.345 2.427

C -0.838 0.237 0.651

N -1.906 -0.547 0.481

C -1.845 -1.96 0.9

C -0.97 -2.141 2.137

C 0.38 -1.471 1.904

N 0.156 -0.094 1.473

H -2.868 -2.29 1.104

H -1.459 -1.701 3.013

H 0.981 -1.45 2.818

C -0.784 1.61 0.035

H -0.714 1.464 -1.048

H 0.159 2.064 0.344

C -1.955 2.546 0.397

H -1.621 3.575 0.222

H -2.177 2.47 1.469

C -3.225 2.298 -0.428

H -3.979 3.052 -0.17

H -2.984 2.45 -1.489

C -3.836 0.901 -0.261

H -4.208 0.768 0.763

H -4.703 0.814 -0.927

C -2.88 -0.252 -0.59

H -3.454 -1.171 -0.728

H -2.328 -0.09 -1.524

H 0.937 -1.987 1.109

H -0.833 -3.21 2.327

169 | P a g e

H -1.441 -2.529 0.052

H 0.985 0.507 1.419

C 3.411 -0.595 -0.077

O 1.031 -1.238 -0.087

H 3.504 -0.657 1.002

H 4.366 -0.777 -0.571

Br 2.977 1.303 -0.475

C 2.33 -1.53 -0.607

H 2.224 -1.349 -1.687

C 2.74 -2.994 -0.397

H 3.66 -3.222 -0.952

H 2.891 -3.198 0.668

H 1.939 -3.645 -0.771

C -1.853 0.092 -0.253

N -2.81 0.663 0.476

C -2.645 2.024 1.025

C -1.711 2.858 0.154

C -0.433 2.071 -0.11

N -0.787 0.772 -0.678

H -3.638 2.485 1.076

H -2.202 3.101 -0.795

H 0.215 2.583 -0.823

C -2.025 -1.319 -0.75

H -2.055 -1.976 0.124

H -1.112 -1.584 -1.281

C -3.262 -1.521 -1.651

H -3.083 -2.414 -2.261

H -3.354 -0.681 -2.352

C -4.574 -1.717 -0.876

H -5.385 -1.932 -1.584

H -4.472 -2.609 -0.24

C -4.983 -0.531 0.005

H -5.221 0.344 -0.615

H -5.9 -0.792 0.55

C -3.923 -0.128 1.037

H -4.375 0.5 1.806

H -3.512 -1.002 1.551

H 0.136 1.906 0.812

H -1.482 3.798 0.664

170 | P a g e

H -2.253 1.935 2.048

H 0.015 0.154 -0.848

C 0.792 -1.246 1.388

O 1.737 -1.606 2.089

O -0.37 -0.87 1.634

C -3.053 -0.558 0.05

O -0.933 -1.391 1.022

H -2.758 -0.862 -0.952

H -4.135 -0.574 0.175

Br -2.586 1.381 0.189

C -2.356 -1.389 1.122

H -2.546 -0.919 2.097

C -2.939 -2.813 1.14

H -4.021 -2.786 1.325

H -2.743 -3.325 0.195

H -2.462 -3.37 1.956

C 1.479 0.572 -0.3

N 2.637 0.038 -0.687

C 2.737 -0.561 -2.035

C 1.902 0.21 -3.053

C 0.469 0.33 -2.55

N 0.499 0.817 -1.169

H 3.792 -0.552 -2.322

H 2.331 1.208 -3.214

H -0.109 1.044 -3.143

C 1.217 0.939 1.135

H 1.122 -0.01 1.674

H 0.229 1.397 1.178

C 2.252 1.872 1.79

H 1.77 2.331 2.661

H 2.497 2.694 1.104

C 3.534 1.17 2.252

H 4.168 1.89 2.784

H 3.264 0.39 2.978

C 4.342 0.53 1.117

H 4.713 1.305 0.43

H 5.226 0.036 1.543

C 3.573 -0.523 0.312

H 4.282 -1.124 -0.26

171 | P a g e

H 3.013 -1.215 0.95

H -0.042 -0.641 -2.554

H 1.92 -0.32 -4.01

H 2.39 -1.599 -1.946

H -0.378 1.134 -0.774

C -0.29 -1.968 -0.133

O -1 -2.198 -1.127

O 0.937 -2.088 0.044

C 3.24 -0.141 0.005

O 1.318 -0.279 -1.554

H 2.933 -1.032 0.547

H 4.319 0.007 0.046

Br 2.503 1.406 1.043

C 2.734 -0.149 -1.433

H 2.937 0.834 -1.874

C 3.49 -1.215 -2.239

H 4.562 -0.988 -2.275

H 3.341 -2.205 -1.803

H 3.102 -1.219 -3.261

C -1.438 0.173 0.478

N -2.532 -0.568 0.302

C -2.598 -1.909 0.921

C -1.909 -1.931 2.282

C -0.488 -1.399 2.139

N -0.537 -0.13 1.407

H -3.654 -2.172 1.024

H -2.473 -1.319 2.996

H -0.03 -1.206 3.113

C -1.175 1.405 -0.343

H -0.948 1.047 -1.355

H -0.247 1.848 0.022

C -2.293 2.466 -0.347

H -1.841 3.413 -0.663

H -2.658 2.624 0.677

C -3.464 2.144 -1.281

H -4.163 2.99 -1.289

H -3.079 2.047 -2.305

C -4.226 0.865 -0.918

H -4.708 0.974 0.063

172 | P a g e

H -5.029 0.712 -1.649

C -3.364 -0.402 -0.911

H -4.013 -1.279 -0.939

H -2.706 -0.468 -1.784

H 0.144 -2.092 1.571

H -1.889 -2.957 2.66

H -2.114 -2.603 0.223

H 0.317 0.422 1.396

C 0.658 -1.473 -1.098

O 1.315 -2.259 -0.383

O -0.535 -1.501 -1.456

C 3.24 -0.141 0.006

O 1.319 -0.281 -1.554

H 2.933 -1.031 0.549

H 4.319 0.008 0.048

Br 2.502 1.408 1.042

C 2.735 -0.15 -1.432

H 2.938 0.832 -1.874

C 3.492 -1.218 -2.236

H 4.563 -0.991 -2.272

H 3.341 -2.207 -1.8

H 3.104 -1.222 -3.259

C -1.438 0.172 0.477

N -2.532 -0.568 0.301

C -2.599 -1.909 0.919

C -1.91 -1.931 2.281

C -0.489 -1.399 2.139

N -0.537 -0.131 1.406

H -3.655 -2.173 1.021

H -2.476 -1.319 2.994

H -0.033 -1.206 3.114

C -1.174 1.405 -0.344

H -0.949 1.046 -1.356

H -0.246 1.847 0.021

C -2.292 2.466 -0.347

H -1.84 3.413 -0.663

H -2.656 2.624 0.678

C -3.464 2.145 -1.28

H -4.162 2.991 -1.287

173 | P a g e

H -3.079 2.048 -2.305

C -4.226 0.866 -0.918

H -4.707 0.974 0.064

H -5.029 0.714 -1.649

C -3.364 -0.401 -0.912

H -4.013 -1.278 -0.941

H -2.706 -0.466 -1.786

H 0.144 -2.093 1.573

H -1.891 -2.957 2.659

H -2.113 -2.603 0.222

H 0.317 0.42 1.396

C 0.659 -1.474 -1.096

O 1.315 -2.258 -0.379

O -0.534 -1.502 -1.456

C -3.02 1.238 0.681

O -1.366 1.863 -0.857

H -3.328 0.247 1.019

H -3.741 2.008 0.973

Br -2.148 -2.149 -0.136

C -2.697 1.252 -0.824

H -2.576 0.227 -1.182

C -3.65 2.05 -1.686

H -4.642 1.587 -1.652

H -3.731 3.084 -1.334

H -3.313 2.057 -2.727

C 1.342 -0.401 0.155

N 2.421 0.287 0.555

C 2.625 0.569 1.988

C 2.024 -0.532 2.859

C 0.571 -0.764 2.459

N 0.498 -0.936 1.013

H 3.703 0.643 2.16

H 2.594 -1.459 2.731

H 0.157 -1.664 2.92

C 1.046 -0.601 -1.309

H 0.786 0.378 -1.732

H 0.144 -1.216 -1.37

C 2.185 -1.255 -2.118

H 1.737 -1.683 -3.021

174 | P a g e

H 2.597 -2.098 -1.549

C 3.304 -0.292 -2.531

H 4.015 -0.82 -3.178

H 2.868 0.512 -3.142

C 4.068 0.34 -1.361

H 4.611 -0.431 -0.799

H 4.821 1.031 -1.761

C 3.184 1.129 -0.387

H 3.808 1.775 0.233

H 2.487 1.788 -0.917

H -0.063 0.085 2.742

H 2.091 -0.241 3.912

H 2.166 1.539 2.211

H -0.356 -1.421 0.63

C -0.86 1.944 0.384

O -1.754 1.556 1.314

O 0.267 2.304 0.639

C -2.117 -0.759 -0.318

O -0.347 -1.724 0.969

H -1.419 -0.338 -1.01

H -3.072 -1.069 -0.713

Br -2.834 1.514 0.071

C -1.673 -1.173 1.074

H -1.559 -0.294 1.708

C -2.642 -2.151 1.73

H -3.616 -1.672 1.87

H -2.765 -3.04 1.106

H -2.254 -2.452 2.707

C 1.063 0.811 -0.227

N 2.001 -0.063 -0.559

C 2.179 -0.504 -1.96

C 1.7 0.566 -2.938

C 0.295 1.024 -2.563

N 0.281 1.386 -1.145

H 3.245 -0.698 -2.104

H 2.382 1.424 -2.918

H -0.014 1.901 -3.137

C 0.873 1.238 1.203

H 0.666 0.34 1.794

175 | P a g e

H -0.023 1.861 1.248

C 2.095 1.987 1.78

H 1.748 2.576 2.635

H 2.47 2.707 1.04

C 3.226 1.06 2.248

H 4.023 1.667 2.695

H 2.839 0.417 3.05

C 3.829 0.164 1.155

H 4.335 0.775 0.395

H 4.599 -0.472 1.61

C 2.814 -0.757 0.468

H 3.311 -1.573 -0.055

H 2.135 -1.238 1.176

H -0.434 0.225 -2.75

H 1.705 0.159 -3.953

H 1.644 -1.453 -2.078

H -0.558 1.856 -0.793

C -0.175 -2.499 -0.2

O -1.203 -2.498 -0.959

O 0.931 -3.011 -0.357

C 2.905 -0.773 0.746

O 2.206 -0.742 -1.587

H 2.79 -1.857 0.713

H 3.698 -0.49 1.439

Br 1.231 -0.095 1.586

C 3.128 -0.213 -0.661

H 3.054 0.885 -0.615

C 4.536 -0.602 -1.125

H 5.31 -0.202 -0.461

H 4.631 -1.693 -1.167

H 4.698 -0.212 -2.134

C -0.981 0.154 -0.747

N -1.812 0.74 0.178

C -1.685 2.172 0.464

C -1.143 2.911 -0.755

C 0.122 2.199 -1.239

N -0.091 0.773 -1.461

H -2.673 2.557 0.739

H -1.896 2.902 -1.553

176 | P a g e

H 0.484 2.641 -2.174

C -1.108 -1.339 -0.955

H -0.817 -1.854 -0.03

H -0.358 -1.602 -1.702

C -2.498 -1.825 -1.415

H -2.37 -2.791 -1.918

H -2.891 -1.133 -2.171

C -3.516 -2.004 -0.28

H -4.447 -2.416 -0.688

H -3.126 -2.758 0.42

C -3.836 -0.728 0.51

H -4.344 0.002 -0.133

H -4.532 -0.98 1.321

C -2.602 -0.051 1.128

H -2.926 0.643 1.909

H -1.966 -0.796 1.624

H 0.923 2.323 -0.494

H -0.938 3.956 -0.498

H -1.017 2.32 1.327

H 1.381 -0.183 -1.616

C 3.54 -0.093 -0.668

O 1.411 -1.228 -0.906

H 3.922 -0.929 -0.083

H 4.351 0.41 -1.196

Br 2.882 1.226 0.663

C 2.424 -0.54 -1.61

H 2.001 0.353 -2.096

C 3.015 -1.462 -2.68

H 3.796 -0.961 -3.263

H 3.442 -2.356 -2.213

H 2.219 -1.781 -3.359

C -1.756 0.086 -0.077

N -2.776 0.896 0.363

C -2.755 2.344 0.116

C -1.689 2.707 -0.914

C -0.401 1.955 -0.572

N -0.627 0.514 -0.549

H -3.748 2.648 -0.239

H -2.022 2.41 -1.916

177 | P a g e

H 0.39 2.167 -1.296

C -1.988 -1.411 -0.051

H -2.129 -1.752 0.983

H -1.064 -1.871 -0.401

C -3.17 -1.876 -0.93

H -3.006 -2.929 -1.186

H -3.152 -1.322 -1.878

C -4.554 -1.751 -0.274

H -5.31 -2.181 -0.943

H -4.563 -2.367 0.637

C -4.968 -0.322 0.102

H -5.087 0.292 -0.802

H -5.948 -0.353 0.596

C -3.968 0.376 1.037

H -4.447 1.234 1.52

H -3.672 -0.302 1.847

H -0.022 2.284 0.406

H -1.534 3.791 -0.92

H -2.571 2.873 1.062

H 0.651 -0.588 -0.757

C 1.673 -1.888 1.792

O 2.783 -2.242 1.682

O 0.563 -1.568 1.969

178 | P a g e

Abbreviation list

ABBCs Carboxylic acid–base bifunctional catalysts

ABMDFP Ammonium bromide modified polyquaternium ionic

liquids

AIBN N-vinylimidazole, azodiisobutyronitrile

[bmim]Br 1-Butyl-3-methylimidazolium Bromide

[bmim]Cl 1-Butyl-3-methylimidazolium chloride

BmimOAc 1-butyl-3-methyl-imidazolium acetate

[BPy]Br Butylpyridinium bromide

BrC2COOH 3-Bromopropionic acid

CABFILs Carboxylic acid-based functional ionic liquids

CCU Carbon Capture Utilization

CCUS Carbon Capture Utilization and Storage

CCS Carbon Capture Storage

CILs Carboxyl-group-functionalized imidazolium-based ionic

liquids

CLPNs Cross-linked polymeric nanogels

CO2 Carbon dioxide

CPC Chloropropene carbonate

CPILM Cross-linked poly (ILs) membranes

[Cnmim]+ Alkyl-substituted imidazolium ions

[Cnpy]+ Alkyl-substituted pyridinium ions

DABCO 1,4-diazabicyclo[2.2.2]octane

DBPILs Bifunctional protic ionic liquids

DBU Diazabicyclo [5.4.0] undec-7-ene

[DBUH]C1 DBU hydrochloride

DFP Dicyandiamide–formaldehyde polymer

DFT Density functional theory

DILA DU based ionic liquids containing aluminium

DMAP 4-dimethylaminopyridine

[DMAPH]Br 4-(dimethylamino) pyridine hydrobromide

DMF Dimethylformamide

179 | P a g e

DPP-MnCl Diphenylporphyrin]manganese(III) chloride

DVB Divinylbenzene

EC Ethylene carbonate

[emim][BF4] 1-Ethyl-3-methylimidazolium hexafluorophosphate

EtOH ethyl alcohol

FT-IR Fourier transform infrared spectrometer

GC-MS Gas chromatography- mass spectrometry

GP Glycidyl phenyl

HBD Hydrogen bond donor

H-bond Hydrogen bond

HEMIMB 1-(2-hydroxyethyl)-3-methylcarbazole bromide

ILs Ionic liquids

KI Potassium iodide

MOF Metal-organic framework

MPILs Metalloporphyrin ionic liquids

MTBD 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene

NMR Nuclear magnetic resonance instrument

[NRxH4-x]+ Alkyl-substituted quaternary ammonium ions

NTF2 Bis(trifluoromethanesulphonyl)imide

2-PAE 2-(phenylamino) ethanol

PBA Poly(butyl acrylate)

PC Propylene carbonate

P-CD P-cyclodextrin

PILs Protic ionic liquids

PO Propylene oxide

POP-TPP Metal porphyrin based porous organic polymer

[PRxH4-x]+ Alkyl-substituted quaternary phosphonium ions

PTAT Phenyltrimethylammonium tribromide

RTILs Room temperature ionic liquids

SC Styrene carbonate

SEM scanning electron microscope

SO Styrene oxide

TAPS Tetraarylphosphonium salts

180 | P a g e

TBAB Tetrabutylammonium bromide

TBD 1,5,7-triazabicyclo[4.4.0]dec-5-ene

TGA Thermogravimetric analysis

TMG Tetramethyl guanidine

TOF Turnover frequency

TON Turnover number

TPP 5,10,15,20-tetra(4-pyridyl)-21H, 23H-porphine

ZIF-8 Zeolitic imidazole framework-8

ZnTPP Zinc 5,10,15,20-tetra(4-pyridyl)-21H, 23H-porphine

β-CD β-cyclodextrin

181 | P a g e

Peer reviewed journal articles

➢ Xianglei Meng, Hong-Yan He, Yi Nie, Xiang-ping Zhang, Suo-jiang Zhang and Jianji Wang.

Temperature-Controlled Reaction–Separation for Conversion of CO2 to Carbonates with

Functional Ionic Liquids Catalyst. ACS Sustainable Chem. Eng., 2017, 5, 3081 (IF=6.970)

➢ Xianglei Meng, Zhaoyang Ju, Suojiang Zhang, Xiaodong Liang , Nicolas von Solms and

Xiangping Zhang,. Efficient Transformation of CO2 to Cyclic Carbonates by Bifunctional Protic

Ionic Liquids under Mild Conditions. Green Chem., (DOI: 10.1039/c9gc01165j) (IF=9.405)

➢ Xue Liu, Yi Nie, Xianglei Meng, Zhenlei Zhang, Xiangping Zhang and Suojiang Zhang DBN-

based ionic liquids with high capability for the dissolution of wool keratin. RSC Adv., 2017, 7,

1981. (IF=2.936)

➢ Zhibo Zhang, Jiahuan Tong, Xianglei Meng, Yingjun Cai, Feng Huo, Jianquan Luo, Suojiang

Zhang and Pinelo Manuel. Development of Novel Porphyrin-Based Ionic Liquids as biomimetic

light-harvesting for High Performance Enzymatic Conversion of Methanol from CO2. Green

Chem., (In peer review) (IF=9.405)

➢ Xianglei Meng, Ting Song, Xiaodong Liang, Xiangping Zhang, Suojiang Zhang and Nicolas von

Solms. Aluminum-containing Ionic Liquid for Cycloaddition of CO2 with Epoxides under Mild

Conditions. Catalysis Science & Technology (for submiting)

➢ Ting Song, Xianglei Meng, Xiangping Zhang, Suojiang Zhang, Peter Szaboa and Anders E.

Daugaard. Poly(Vim-co-BuA) membrane used for CO2 conversion into cyclic carbonates (Co-

first author for submiting)

Conference presentations

➢ Efficient Transformation of Atmospheric CO2 to Carbonates by DBU Based Ionic Liquids under

mild conditions. (Oral), CERE Annual Discussion Meeting, Denmark, June, 2018.

➢ Biological Porphyrin Ionic Liquids as Photocatalysts for Conversion of CO2 to Carbonates

(Poster), CERE Annual Discussion Meeting, Denmark, June, 2018.

➢ Efficient Transformation of CO2 to Carbonates by Functional Ionic Liquids under Mild Conditions.

(Poster), 9th Trondheim Conference on Carbon Capture, Transport and Storage. Norway, May,

2017

➢ Efficient Transformation of CO2 to Carbonates by Functional Ionic Liquids under Mild

Conditions. (Poster), CERE Annual Discussion Meeting, Denmark, June, 2017.

➢ The absorption and activation of CO2 by functional ionic liquids and it’s conversion at mild

conditions.

(Poster), CERE Annual Discussion Meeting, Denmark, June, 2016.

http://pubs.rsc.org/en/results?searchtext=Author%3AXue%20Liu

http://pubs.rsc.org/en/results?searchtext=Author%3AYi%20Nie

http://pubs.rsc.org/en/results?searchtext=Author%3AXianglei%20Meng

http://pubs.rsc.org/en/results?searchtext=Author%3AZhenlei%20Zhang

http://pubs.rsc.org/en/results?searchtext=Author%3AXiangping%20Zhang

http://pubs.rsc.org/en/results?searchtext=Author%3ASuojiang%20Zhang

Center for Energy Resources Engineering Department of Chemical and Biochemical Engineering Technical University of Denmark

Søltofts Plads, Building 2292800 Kgs. LyngbyDenmarkPhone: +45 45 25 28 00

www.kt.dtu.dk

conversion of co2 to carbonates catalyzed by ionic liquids ......conversion of co2 to carbonates...

Documents