| In today's society,with the progress of the times and the development of science and technology,our requirements for energy are increasing.As a very clean energy source,hydrogen has always attracted people's attention.In addition,we usually think that sunlight is inexhaustible.It is inexhaustible,but it has not been fully developed and utilized,so it has great potential.Therefore,it is very meaningful to realize the conversion of light energy into chemical energy.In May 2018,the Chinese Association for Science and Technology organized a collection of 60 major For scientific issues and major engineering technical problems,five problems were selected in the field of materials,and photocatalytic materials were one of them.As an important branch in the field of photocatalysis,hydrogen production by photolysis of water has always been the focus of research by scientists.However,since the first realization of hydrogen production by photolysis of water in the 1970s,the development of this field has been relatively slow.With the rise of porous materials,more and more people regard new materials like covalent organic frameworks as carriers for photocatalysis experiments,and strive to find new breakthroughs through continuous exploration of the types of materials.As a pure organic porous polymer,the covalent organic framework material has diverse structures,designability,crystallinity,and good stability.It has a large specific surface area and low density.These characteristics make it meet the needs of catalytic reactions.It is very consistent,so this paper uses this as a basis to design and synthesize two kinds of covalent organic framework materials,and to explore the performance of their photolysis of water to hydrogen.In the second chapter,we chose phenothiazine,a butterfly-shaped molecule,and introduced it into the framework of covalent organic framework materials for the first time.After the precursor synthesis,we used 10-methyl-phenothiazine-3,7-dicarbaldehyde(MPTz)and the commonly used ligand 1,3,5-tris(4-aminophenyl)benzene(TAPB)in the covalent organic framework undergoes Schiff base reaction to obtain TAPB-MPTz-COF.The hydrogen production rate is 115?mol g-1 h-1,which is a relatively moderate level among covalent organic framework materials.According to theoretical simulations Compared with powder X-ray diffraction analysis,the judgment is mainly due to the 157.5°dihedral angle between the two benzene rings of phenothiazine.This non-planar structure is not conducive to the transfer of electron-hole pairs,although TAPB-MPTz-COF has good crystallinity and stability,and its optical band gap is very suitable for photocatalytic reactions,but the rate of hydrogen production still cannot reach a high level.Chapter 3 improves the covalent organic framework material on the basis of Chapter 2.We design a new scheme to use the large planar molecule 1,3,6,8-tetra-(4-aminophenyl)pyrene(TAPP)with stronger flatness to replace TAPB to increase the rate of hydrogen production by photolysis of water.A second brand-new covalent organic framework material TAPP-MPTz-COF was synthesized.The powder X-ray diffraction was compared with theoretical simulations.It is found that this is a one-dimensional strip-shaped covalent organic framework material,similar to TAPB-MPTz-COF,TAPP-MPTz-COF also has suitable electrochemical energy levels and optical band gaps,good stability,and uniformity he morphology and characteristics of TAPP-MPTz-COF ensure that it has the ability to produce hydrogen by photolysis of water.In addition,TAPP-MPTz-COF has a larger specific surface area and a wider range of light absorption,and the final rate of photolysis for hydrogen production is also up to 720?mol g-1h-1 was obtained. |
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