engleski

Nitrogen-containing covalent organic polymers: Synthesis, characterization and computational study

Selective binding of gas molecules is very important in the design of new nanoporous materials with increased potential for CO2 capture and air separation. Covalent organic frameworks (COFs) and polymers (COPs) complement other porous materials, such as zeolites, MOFs (metal-organic frameworks), etc., and have shown excellent potential for the gas storage and separation, catalysis, and usage in optoelectronics. Choosing precursor molecules of precisely defined geometry, functionality and selectivity can result with spontaneous association of molecules into 2D or 3D amorphous COPs or crystalline COFs.[1] A series of new azo-bridged COPs was successfully synthesized by condensation reactions of 1, 3, 5-tris(4- nitrophenyl)benzene and various aromatic diamino compounds used as linkers. Their structural and thermal features were characterized by using different experimental techniques. A computational strategy to investigate the potential of precursor molecules toward selective binding of N2 and CO2 in these systems were developed. A detailed conformational search was performed with molecular mechanics, and the resulting complexes were reoptimized by the DFT method in vacuum, and finally, binding energies of N2 and CO2 were calculated for each of the obtained complexes. The various aromatic building blocks were divided in two groups: (i) central units composed of three phenyl rings attached to nitrogen, benzene, pyridine and triazine, (ii) linkers including biphenyl and those in which two phenyl rings were separated by oxygen, sulphur, carbonyl, one and two methylene groups. In addition, the effect of different types of bonds (azo, azoxy, azodioxy) on N2 and CO2 binding was investigated. A greater selectivity toward CO2 binding in comparison to N2 was confirmed in our calculations for all of the investigated complexes.

covalent organic polymers, nanoporous materials, molecular mechanics, DFT, gas storage, gas separation

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