covalant organic frameworks

Bionano Chemistry Lab

Muhammad Ehsan(2013652616)

Date: 2013-12-05

Types of Bonding

Ionic Bonds

Covalent Bonds

Coordinate Bonds

Dipole Interactions

Van der Walls forces

Pi-Pi Stacking

Introduction

Covalent Organic Frameworks (COFs)

Covalent organic frameworks (COFs) represent an exciting new type of porous organic

materials, which are ingeniously constructed with organic building units via strong covalent

bonds.

Metal-Organic Frameworks (MOFs) are compounds consisting of metal ions or cluster

coordinated to often rigid organic molecules to form one-, two-, or three-dimensional

structures that can be porous.

Why to Synthesize COFs

Driving Force for the Synthesis of COFs:

Bringing

i) Covalent linkage

ii) Porosity and

iii) Crystallinity

within the same material

COFs posses

i) Low density

ii) Large surface area

iii) Tuneable pore size

iv) Facilely tailored functionality

v) Versatile covalent combination

Basic Concern

Covalent Bond Formation

Building Units

Classification of COFs

Depending on the building block dimensions, COFs can be categorized into

two-dimensional (2D)

three-dimensional (3D) COFs.

In 2D COFs, the covalently bound framework

is restricted to 2D sheets.

three-dimensional (3D) COFs.

In contrast, 3D COFs, which extend this framework three dimensionally

through a building block containing an sp3 carbon or silane atom,

characteristically possess high specific surface areas

Design and synthesis

Structure of building blocks

To obtain a crystalline and ordered COF, the structure of the building blocks

must meet two requirements:

the formation reaction of the COF should be a reversible reaction.Contain reactive groups,

monomers, oligomers, and polymers

the geometry of the building blocks should be well preserved in the COF.

building blocks should be conformationally rigid,

and the bond formation direction must be discrete.

Synthetic Methods

Solvothermal synthesis Microwave synthesis

Solvothermal synthesis

Monomers and mixed solvents

are placed in a Pyrex tube

Degassed via several

freeze–pump–thaw cycles

The tube is then sealed

and heated to a designated

temperature for a certain reaction

time.

The precipitate is collected,

washed with suitable solvents,

dried under vacuum to

yield the COF as solid powder.

Solvent combinations and ratios are important factors in balancing between framework

formation and crystallization when synthesizing highly crystalline COFs.

A suitable temperature is important to ensure the reversibility of the reaction. (85–120 0C)

Factors Affecting the Solvothermal Synthesis

Microwave Synthesis

Microwave synthesis provided several advantages over solvothermal

methods.

Produces COFs rapidly. Thus, large-scale synthesis is possible.

A sealed vessel is not required for the microwave synthesis.

Synthesis of monolayers on metal surfaces.

Synthesis of monolayers on a (highly ordered pyrolytic graphite)

HOPG surface

Synthesis of oriented thin films on graphene surfaces.

Ionothermal synthesis

Room-temperature synthesis

Other Synthetic Methods

Structural Studies of COFs

XRD, crystalline structure

Infrared spectroscopy

Solid-state NMR spectroscopy

Elemental analysis

X-ray photoelectron spectroscopy

are all useful for evaluating the linkages, terminal

groups, and compositions of the COFs.

Some Examples of COFs

Figure .(a) Schematic representation of T-COF 1 (left) and T-COF-3 based on thiophene based

building blocks, reproduced with permission from, copyright 2013 by the National Academy of Sciences of

the United States of America

Some Examples of COFs

Figure (a) Co-condensation of a truncated linker and a tetraboronic acid results in the functionalized 3D COF-102,

reproduced with permission from, copyright 2012 by John Wiley Sons, Inc.,

Some Examples of COFs

Fig. Co-condensation of monomers 11 and 21 to synthesize 2D HHTP-DPB COF and the proposed crystalline structure.

(Adapted with permission from Copyright 2011 American Chemical Society.)

The function of a COF arises from its porosity and molecular

skeletons

1. Gas adsorption and storage

• Hydrogen

• Methane

• Carbon dioxide

• Ammonia

2. Heterogeneous catalysis

3. Semiconduction

4. Photoconduction

Applications of COFs

To be continue…….