Synthesis Of Pyridyl Congugated Microporous Polymers And Their Composites For Photocatalysis

Conjugated microporous polymers（CMPs）are a new type of organic semiconductor photocatalyst withπ-πconjugated framework.The advantages of high specific surface area,adjustable forbidden band width,easy functionalization,and diverse synthesis methods make them widely used in the field of photocatalysis.In this paper,pyridyl conjugated microporous polymers（PCMPs）and their Co-S composites and PCMPs/Ti O₂ composites were prepared,and their morphology and structure were characterized,and their hydrogen evolution performance under full spectrum and visible light was explored.The main research content includes the following three parts.（1）In view of the disadvantages of the traditional CMPs synthesis route of high cost and strict conditions,the paper proposes a synthesis reaction based on Chichibabin reaction,which uses aromatic aldehydes and aromatic ketones to undergo polycondensation with ammonium acetate without adding any metal.Six pyridyl conjugated microporous polymers（PCMPs）were prepared by choosing two aromatic ketones and three aromatic aldehyde monomers.Different conjugated frameworks were constructed through the selection of different monomers.The chemical structure was confirmed by infrared spectroscopy,X-ray diffraction,nuclear magnetic resonance spectroscopy,and X-ray photoelectron spectroscopy.The pore structure was analyzed by a specific surface area analyzer.Ultraviolet absorption spectroscopy and cyclic voltammetry curves determine their energy band structures.Use an all-glass automatic online trace gas analysis system to test its photocatalytic hydrogen evolution performance.The results showed that the PCMPs were successfully prepared without adding a metal catalyst.The specific surface area of PCMP33-3 was as high as 523 m²·g^-1,and the pore diameter of PCMPs was basically below 2 nm.The hydrogen evolution rate of polymers is related to the forbidden band width and porous properties of polymers.Under full-spectrum irradiation,the average hydrogen evolution rate（HER）can reach as high as 1198.9μmol·g^-1·h^-1,which is an efficient photocatalytic product for green synthesis.（2）In order to reduce the cost of photocatalytic hydrogen evolution,the polymer PCMP23-2 with the highest average hydrogen evolution rate was selected to be compounded with cobalt and sulfone（Co-S）.The resulting composite PC23-2-200 has the average hydrogen evolution rate under the full spectrum without adding a co-catalyst.It can reach 1174.0μmol·g^-1·h^-1,which is basically the same as the pure polymer with platinum promoter(1198.9μmol·g^-1·h^-1).This proves that the composites of Co-S and polymer can effectively replace precious metal promoters,and reduce the costs.At the same time,the effect of different doping amounts on photocatalytic hydrogen evolution was explored.The results showed that when the mass of PCMP23-2 was 100 and 200 mg,the average hydrogen evolution rate of the composite under the full spectrum were 1247.6 and 1174.0μmol·g^-1·h^-1.They can both achieve the same hydrogen evolution efficiency as pure polymer with platinum promoter,and PC23-2-100 can even have better HER.（3）Considering that the polymer cannot achieve high-efficiency hydrogen evolution under visible light,the polymer PCMP33-3 with a wide absorption range is used for in-situ composite with titanium dioxide（Ti O₂）,and the composites with different doping amounts are prepared by changing the addition amount of titanium dioxide.They were also tested for photocatalytic hydrogen evolution under visible light.The study showed that when the doping amount is 500 mg（0.5 mmol relative to aldehyde monomer）,the hydrogen evolution rate under visible light can reach 1070.9μmol·h^-1·g^-1.It is proved that the formation of heterojunction is beneficial to improve the hydrogen evolution efficiency of the photocatalyst.