covalant organic frameworks
TRANSCRIPT
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Bionano Chemistry Lab
Muhammad Ehsan(2013652616)
Date: 2013-12-05
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Types of Bonding
Ionic Bonds
Covalent Bonds
Coordinate Bonds
Dipole Interactions
Van der Walls forces
Pi-Pi Stacking
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Introduction
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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.
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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
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Basic Concern
Covalent Bond Formation
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Building Units
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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.
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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
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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.
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Synthetic Methods
Solvothermal synthesis Microwave synthesis
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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.
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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
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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.
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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
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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.
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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
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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.,
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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.)
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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