The Construction Of Covalent Organic Framework Materials And Their Catalytic Carbon Dioxide Conversion Applications

Covalent organic frameworks（COFs）are an emerging class of crystalline and porous materials,which are formed by the covalent bonding of various organic monomers.COFs feature low mass densities,high specific surface areas,regular pore structures,high thermal and chemical stabilities as well as tailorable functionalities,they have potential applications in diverse fields,such as gas adsorption,heterogeneous catalysis and photoelectrics.This dissertation is mainly focused on the synthesis of task-specific COFs for the cycloaddition reaction of carbon dioxide and epoxides into cyclic carbonate.The relationship between COFs structure and catalytic performance has been established at the molecular level by studying the characterization of COFs and their catalytic performance,which provides new research ideas for the synthesis of new COFs and the expansion of the application scope.The following are the main contents:In Chapter one,we have mainly summarized the research advances of COFs materials.We have introduced their types,synthetic methods and potential applications in gas adsorption and separation,heterogeneous catalysis,lithium-sulfur batteries and proton conduction.In Chapter two,we have prepared a composite COF containing linear ionic polymer,TT-COF was first synthesized by the condensation reaction of 1H-1,2,4-triazole-3,5-diamine and 2,4,6-trihydroxy-benzene-1,3,5-tricarbaldehyde via a interfacial crystallization strategy.1-Vinyl-3-ethylimidazolium bromide was adsorbed into TT-COF and subsequent free radical polymerization generated the linear ionic polymer in TT-COF.The catalytic application of resultant composite in the cycloaddition reaction of carbon dioxide and epoxides into cyclic carbonates has been investigated.The composite shows much higher catalytic activity than TT-COF,linear ionic polymer and their physical mixture.The enhanced catalytic activity is mainly attributed that CO₂-philic groups in TT-COF enrich and activate CO₂,while bromide anions in the linear polymer facilitate the ring opening of the epoxides through nucleophile attack,thus resulting in high catalytic efficiency.In Chapter three,we prepared an anionic COF material based on polyoxomolybdates（POM）.Firstly,we synthesized one ionic ligand containing polyoxomolybdate and amine groups,subsequentSchiff-basedcondensationreactionwith1,3,5-tris（4-formylphenyl）benzene gave rise to POM-COF.POM-COF exhibits good catalytic activity and selectivity in the cycloaddition reaction of carbon dioxide and epoxides without extra addition of other catalytic species,which is mainly attributed that polyoxomolybdate nodes in the skeleton of COFs serve as nucleophile for promoting ring opening of the epoxides.