| Covalent organic frameworks（COFs）are a kind of crystalline porous materials that are held together by organic building blocks units through strong covalent bonds.COFs constructed from flexible monomers can generally expand the lattice size,which may help remove contaminants.Covalent organic frameworks which integrate organic photoactive monomers into can form a good photosensitizer.In addition,the introduction of redox active units into the structure of two-dimensional COFs can also impart excellent pseudocapacitance properties to the material.These unique properties are a great significance to the synthesis and application of covalent organic framework materials.In our research,we will pre-design the covalent organic framework’s stacking method,channel size,functional group,etc,and study its various properties.1.COFs with flexible,nitrogen-rich structure and electron-richπ-πconjugated system can provide effective binding sites for the adsorption of pollutants,and have good application value in environmental remediation.In the second chapter of our work,we synthesized a flexible,nitrogen-rich COF material（TPT-DMBD-COF）,which has good stability,high porosity,and abundant N atom sites.Through the research,it is found that it has a strong adsorption effect on methylene blue（MB）and has excellent recyclability.Based on the study of the adsorption of MB on TPT-DMBD-COF,we propose a reasonable adsorption mechanism to explain the entire adsorption process.This research provides a new idea for the removal of dyes in water.2.The covalent organic framework material with photocatalytic activity is a new type of heterogeneous photocatalyst developed in recent years.Most small molecule photosensitizers usually require noble metals（iridium,ruthenium,rhodium,etc.）to have photocatalytic activity and have poor reusability,so they have certain limitations.Therefore,it is a great significance to develop a metal-free and easily recyclable covalent organic framework photocatalyst.In the third chapter of our work,we synthesized a covalent organic framework material（BTT-TPA-COF）with benzothiophene and triphenylamine groups connected by imine bonds.It has good stability,large size,big specific surface area and excellent photoelectric performance,which can efficiently synthesize 2-substituted benzimidazole compounds under visible light irradiation.In addition,the catalyst can be reused and after 8 cycles,the yield can still be maintained above 90%.3.COFs have gradually become ideal energy storage devices because of their high specific surface area and the ability to precisely control the electroactive groups in the pores.In the fourth chapter of our work,we used the condensation reaction of2,6-diaminoanthraquinone and cyanuric chloride to synthesize a two-dimensional COF（CC-DAQ-COF）linked by-NH-bonds.The study showed,CC-DAQ-COF has better stability,larger specific surface area and rich pore structure.As an electrode material for supercapacitors,it has reversible electrochemical activity and good specific capacitance(184.25 F g-1).Therefore,by changing the monomers,the structure and electrochemical performance of the covalent organic framework materials can be effectively improved,thereby providing a new way for the application of covalent organic framework materials in high-performance supercapacitors. |
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