powder diffraction study of zeolitic imidazolate framework-8

l Powder Diffraction Study of Zeolitic Imidazolate Framework-8 l March 2015 l Owen Gledhill

Powder Diffraction Study of Zeolitic Imidazolate Framework-8

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A. Petricola, 2008. Ariel view of the ESRF, Available from: http://www.esrf.eu/decouvrir [Accessed on 13/01/2015]

l Powder Diffraction Study of Zeolitic Imidazolate Framework-8 l March 2015 l Owen Gledhill

ESRF – EUROPEAN SYNCHROTRON RADIATION FACILITY

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ESRF, 2008, ESRF brochure [online]. Grenoble: ESRF. Available from:http://www.esrf.fr/about/information-material/brochures [accessed on: 13/01/2015]

Linac

Booster Synchrotron

Storage Ring

l Title of Presentation l Date of Presentation l Author

SYNCHROTRON ANIMATION

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l Powder Diffraction Study of Zeolitic Imidazolate Framework-8 l March 2015 l Owen Gledhill

PXRD – POWDER X-RAY DIFFRACTION

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2θ

Synchrotron radiation (X-

rays) Powder Sample

Detector

I

ID22

• High resolution powder X-ray diffraction beamline.

• Insertion device used is an undulator:

• Also uses a monochromator.

Bragg’s Law

• Path length difference: AB+BC=2dsinθ

• When reflected waves are in phase, AB+BC=nλ

• This gives Braggs Law:

• Commonly shortened to:

ID22, Technical description [online], Grenoble, ESRF. Available from: http://www.esrf.fr/id22/technical-description [accessed on: 21/01/2015] P.Atkins, J. De Paula; Atkins’ Physical Chemistry; OUP, Oxford, Ninth edn., 2010, 701-704

A

B

C

θ

θ

d

l Title of Presentation l Date of Presentation l Author

PLACEMENT OBJECTIVES

• Research current MOF and ZIF chemistry• Synthesise ZIF 8 using a range of methods• Use PXRD as a characterisation technique• Gas adsorption study of ZIF 8

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Unit cell of ZIF 8 showing pore opening comprised of 6-methylimidazole rings

l Powder Diffraction Study of Zeolitic Imidazolate Framework-8 l March 2015 l Owen Gledhill

INTRODUCTION TO MOFS AND ZIFS

• Metal organic frameworks or MOFs are comprised of metal ions or clusters coordinated to organic molecules

• Zeolitic imidazolate frameworks or ZIFs are a subclass of MOFs. They are made of transition metal ions and imidazolate organic linkers.

• ZIFs have structures analogous to those of naturally occurring alluminosilicate zeolites. M-Im-M (where M represents the transition metal ion) angle is similar to that of the 145o Si-O-Si found in zeolites.

• MOFs and ZIFs are highly porous with large surface areas and hence have potential applications in gas storage and catalysis.

• ZIFs have particularly high chemical and thermal stability.

• ZIF 8 is Zn2+ ions with 2-methylimidazole linkers. It takes the form Zn(mIm)2

• ZIF 8 has the space group I3m (no.217)

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l Powder Diffraction Study of Zeolitic Imidazolate Framework-8 l March 2015 l Owen Gledhill

DIFFERENT SYNTHETIC METHODS

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Solvothermal• Reagents are a hydrated metal salt and the

chosen imidazole linker• Organic solvents or alcohols • High yields and near stoichiometric ratio of

ragents• More expensive and more difficult to dispose of

solvents etc…

Hydrothermal• Reagents are a hydrated metal

salt and the chosen imidazole linker

• Water as solvent• More environmentally friendly

option• Requires a large excess of the

linker molecule

Dimethylformamide (DMF) method1:• Zn(NO3)2∙6H2O (14mmol), 2-methylimidazole

(11.7mmol)• Heated in a programmable oven• Precipitate collected by filtrationEthanol/Acetone method2:• Zn(NO3)2•6H2O and 2-methylimidazole (1:8 molar ratio)• Precipitate collected by centrifugation

1. K.S. Park, Z. Ni, A.P. Côté, J.Y. Choi, R. Huang, F.J. Uribe-Romo, H.K. Chae, M. O’Keeffe, O.M. Yaghi; Proceedings of the National Academy of Sciences of the United States of America; 2006; vol. 103 no. 27; 10186-101912. E.L. Bustamante, J.L. Fernández, J.M. Zamaro; Journal of Colloid and Interface Science; 2014; vol. 424; 37-433. K. Kida, M. Okita, K. Fujita, S. Tanaka, Y. Miyake; CrystEngComm; 2013; vol. 15 no. 9; 1794-1801

Aqueous method3:• Used Zn(NO3)2•6H2O (2.5mmol) and 2-

methylimidazole (25mmol)• Heated in a programmable oven• Precipitate collected by filtration

l Powder Diffraction Study of Zeolitic Imidazolate Framework-8 l March 2015 l Owen Gledhill

DIMETHYLFORMAMIDE (DMF) SYNTHESIS

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2θ

I

• λ = 0.496Å• 0.9mm capillary• Indexed using DASH 3.2 to give a cubic unit cell with lattice parameter 17.032Å• Simulated pattern lattice parameter 16.991Å

OG1b diffraction pattern collected on ID22

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0

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20

30

40

50

60

70

80

90

100

10 20 30

Intensity

2-theta

ZIF 8 cubic (Sim) Observed Reflections Empirical with Pawley refinement Simulated ZIF 8 pattern*

*K.S. Park, Z. Ni, A.P. Côté, J.Y. Choi, R. Huang, F.J. Uribe-Romo, H.K. Chae, M. O’Keeffe, O.M. Yaghi; Proceedings of the National Academy of Sciences of the United States of America; 2006; vol. 103 no. 27; 10186-10191

l Powder Diffraction Study of Zeolitic Imidazolate Framework-8 l March 2015 l Owen Gledhill

DMF ANALYSIS – PAWLEY REFINEMENT

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Section of jEdit file with ZnO structural information

2θ

I

Pawley refinement including ZnO structural information

• Impurity is ZnO• Can be accounted for using ZnO .cif file• Pawley refinement run in TOPAS using input file

from jEdit• Unit cell parameter refined to 17.016Å

l Powder Diffraction Study of Zeolitic Imidazolate Framework-8 l March 2015 l Owen Gledhill

DMF ANALYSIS – RIETVELD REFINEMENT

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2-methylimidazole z-matrix

OG1 diffraction pattern with Reitveld refinement ZIF-8 structure

• Rietveld refinement uses structural information to fit the pattern.• All peaks are fit • Sharp peaks show the sample is highly crystalline.

Z matrices• Rigid body• Defines the position of certain

atoms with respect to others• Uses a combination of bond

lengths and angles• In this case, 2-methylimidazole

has been defined using a z-matrix

I

2θ

2-methylimidazole rigid body

l Powder Diffraction Study of Zeolitic Imidazolate Framework-8 l March 2015 l Owen Gledhill

AQUEOUS SYNTHESIS AND ANALYSIS

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I

2θ

• Using the example of OG2. λ = 0.401Å. 1.0mm capillary.• Indexed using DASH 3.2 to give an orthorhombic unit cell with parameters: a= 24.057Å, b= 19.673Å, c=

16.983Å. • Space group P222 was used for Pawley refinement.• It is clearly not ZIF 8.

-10

0

10

20

30

40

50

60

70

80

90

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10 20 30

Intensity

2-theta

ZIF 8 cubic (Sim) Observed Reflections

Simulated

Empirical

l Powder Diffraction Study of Zeolitic Imidazolate Framework-8 l March 2015 l Owen Gledhill

ETHANOL/ACETONE SYNTHESIS AND ANALYSIS

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2θ2θ

I I

• λ=0.345Å. 1.0mm capillary• Indexed to give lattice

parameter 16.991Å • Pawley and Rietveld

refinement run using space group I4̅3m

• Lattice parameter refined to 16.581Å

Ethanol with Rietveld

Acetone with Rietveld

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0

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70

80

90

100

10 20 30

Intensity

2-theta

ZIF 8 cubic (Sim) Observed Reflections

Simulated

• λ=0.345Å. 1.0mm capillary

• Indexed to give lattice parameter 17.006Å

• Pawley and Rietveld refinement run using space group I4̅3m

• Lattice parameter refined to 16.619Å

l Powder Diffraction Study of Zeolitic Imidazolate Framework-8 l March 2015 l Owen Gledhill

COMPARISON OF SYNTHETIC METHODS

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Synthetic method DMF Aqueous Ethanol/Acetone

Lattice type Cubic Orthorhombic Cubic

Space group I4̅3m P222 I4̅3m

Lattice parameter(s), (Å)

a=b=c=17.016 a=24.057, b=19.673, c=16.983 a=b=c=16.581 (ethanol)a=b=c=16.619 (acetone)

Diffraction Pattern

2θ

I Ethanol

2θ

I Acetone

I

2θ

I

2θ

l Powder Diffraction Study of Zeolitic Imidazolate Framework-8 l March 2015 l Owen Gledhill

GAS ADSORPTION STUDY/PLANS FOR GAS ADSORPTION STUDY

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• CO2 adsorbed onto sample at various pressures• Analysis will be to try and understand where the molecules lie in the framework• Will look to do further measurements with other gases.

l Powder Diffraction Study of Zeolitic Imidazolate Framework-8 l March 2015 l Owen Gledhill

CONCLUSION SO FAR AND PLANS FOR REST OF THE PLACEMENT

Conclusions• Wide range of synthetic routes• DMF method was most suitable for this study:• Sharp peaks

• Correct lattice parameter

• Uses sensible amounts of reagents

• Gas adsorption• Initial look shows gas was adsorbed into the pores

Future Plans• Further gas adsorption measurements• Repeat measurements

• Further measurements with different gases

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l Powder Diffraction Study of Zeolitic Imidazolate Framework-8 l March 2015 l Owen Gledhill

ACKNOWLEDGEMENTS

• ESRF – European Synchrotron Radiation Facility• In particular:• Christina Drathen

• Andy Fitch

• All the staff on ID22

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l Title of Presentation l Date of Presentation l Author

PROBLEMS FACED SO FAR…

• Samples had a very short lifetime in the beam.

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3 three minute scans run at the same position on the capillary

ZnO peak (left) with and ZIF 8 peak (right)

l Title of Presentation l Date of Presentation l Author

WHAT IS A SPACE GROUP?

• Categories developed by mathematical group theory• Describe the symmetry elements for unit cells

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