Synthesis,Structural Control And Photocatalytic Hydrogen Production Of Covalent Triazine Framework

Covalent triazine frameworks（CTFs）are porous organic polymers with aromatic triazine rings as the linkage units.CTFs exhibit excellent stability,high specific surface area and low density.Moreover,there are strong conjugation effects between the triazine rings and the benzene rings,and the building units can be flexibly adjusted to tune the photoelectric properties.These advantages of CTFs make it applied in photocatalysis.At present,although tremendous progress in photocatalytic water splitting for produce hydrogen using CTFs have been made,the severe photo-generated charge recombination still restricts the photocatalytic performance of CTFs,and most studies focused on sacrificial water splitting.Also,the limitations of synthesis methods and monomers hinder CTFs practical application.In order to address these problems,we developed a simple method to adjust the structure and inhibit charge recombination,and developed a new method to construct CTFs with different structures,and explored their performance in the field of photocatalytic biomass reforming for hydrogen production.The main research contents are as follows:（1）A simple and effective structure control strategy of CTFs was developed.In this work,cyano group was successfully introduced into the polymers by simple copolymerization method,and the microstructure of the photocatalyst was further regulated by adjusting the monomer ratio.Cyano groups exhibit strong electron-withdrawing properties,which can improve the light absorption ability of CTFs,promote the transfer and separation of photogenerated electrons and holes,and thus improve the photocatalytic hydrogen production rate of materials.Fluorescence and photocurrent measurements showed that the recombination of photogenerated electrons and holes in the cyano modified covalent triazine polymer was effectively inhibited compared with CTF-HUST-1,so the photocatalytic performance were significantly improved.The results suggested that CTF-CN-0.75 showed the best performance in photocatalytic hydrogen production,and the hydrogen production rate can be up to 7850μmol h^-1 g^-1,which was 5.4 times higher than that of CTF-HUST-1.This work provides a simple way to adjust the photocatalytic performance of covalent triazine polymers.（2）A new method for synthesis of CTFs by reaction between benzyl halide and amido monomers has been developed,and a series of CTFs were synthesized efficiently.Compared with the reported monomers-nitrile,aldehydes,benzyl alcohol and benzylamine,benzyl halide monomers are important intermediate for synthesis,and are simple to be produced in industry,highly reactive activity and easy to expand structure.The resuliting CTFs samples have high specific surface area,strong light absorption ability and adjustable band structure,and therefore can be used as superior photocatalysts.In the application of photocatalytic hydrogen evolution of CTFs,most of the investigations are,however,focused on sacrificial water splitting,among which the electron donors are used to inhibit the recombination process of photogenerated electrons and holes,and then improve the hydrogen production rate.The photocatalytic biomass reforming is a viable alternative for photocatalytic hydrogen production.This work explored the performance of organic semiconductor CTFs in photocatalytic reforming of glucose,and analyzed the mechanism of glucose reforming and the structure-performance relationship.The highest hydrogen production rate of the synthesized CTFs can reach 330μmol h^-1g^-1.This work offered a new synthesis method for CTFs,provided a simple and easy way for the expansion of various complex structures,and proved the great potential of porous organic semiconductors in the field of photocatalytic biomass reforming.