Study On The Photocatalytic Oxidation Of Benzylamine Coupling With H₂O₂ And H₂ Production

With the rapid development of the global economy,the problem of energy shortage and environmental pollution is increasingly serious,which makes the development of new,green,environmentally friendly of new energy is very important.Photocatalytic organic synthesis coupled hydrogen（H₂）or hydrogen peroxide（H₂O₂）production technology can successfully convert solar energy into hydrogen energy and chemical energy,which is favored by people.However,semiconductor photocatalysts still have the problems of low photocarrier migration efficiency,easy recombination of photogenerated electron-hole and low visible light utilization efficacy,which seriously restrict their further application in the field of photocatalytic organic synthesis.Imines are key intermediates in drug synthesis.The traditional method for synthesizing imines is not only complicated,but also produces some by-products,which are easy to pollute the environment.Photocatalytic oxidation of benzylamine to synthesize imines has attracted wide attention due to its mild reaction conditions,high conversion rate and high selectivity.It is considered as one of the most effective methods for the synthesis of imines.In view of the problems of low photocarrier migration efficiency,easy recombination and low visible light utilization of semiconductor photocatalysts,two kinds of hyper-crosslinked polymer semiconductor photocatalysts were designed and synthesized by adjusting the conjugation degree of monomers and the types of functional groups,and their effects on the catalytic activity of benzylamine oxidation coupling coupled H₂O₂ preparation reaction were studied.In addition,in order to improve the carrier migration and separation efficiency of ZnIn₂S₄（ZIS）based photocatalyst and inhibit the photogenerated electron hole recombination,we constructed a ZIS/CeO₂ heterojunction photocatalyst modified with MoS₂ cocatalyst,MoS₂-ZIS/CeO₂.The catalytic activity of benzylamine to H₂ production by photocatalytic coupling in the absence of oxygen was studied.Specific research contents are as follows:1.Using aromatic monomers（benzene,biphenyls,p-triphenyls and p-tetrabyphenyls）of different conjugated degrees with dimethoxymethane（CH₃O-CH₂-OCH₃,FDA）as crosslinking agent,under the catalysis of Lewis acid（anhydrous FeCl₃）,A series of hypercrosslinked polymer semiconductor photocatalyst HCPs was synthesized by Friedel-Crafts reaction.N2 desorption and O₂ adsorption experiments confirmed that the synthesized HCPs photocatalyst had higher specific surface,abundant pore structure and excellent O₂ adsorption performance,which provided abundant reactive sites and high O₂ concentration for Redox reaction.The UV characterization of solid and photoelectric experiments show that the increase of conjugation of monomer improves the visible light efficiency and photogenic carrier separation efficiency of HCPs.Kinetic experiments and electron paramagnetic resonance（EPR）experiments were used to investigate the mechanism of photocatalytic oxidation of benzylamine coupled with H₂O₂ by HCPs.This work provides a new strategy for the construction of efficient HCPs-based photocatalysts.2.Amino acid modified HLP-HCPs photocatalyst was synthesized by Friedel-Crafts alkylation catalyzed by lewis acid（anhydrous FeCl₃）using L-phenylalanine and hexaphenylbenzene as monomers and FDA as the foreign agent.These HCPs were used as photocatalysts to catalyze the oxidation of benzylamine coupled with H₂O₂ in the presence of O₂.Detailed studies have confirmed that the-NH₂ functional group in HLP-HCPs effectively changes the charge distribution of HCPs,and the effective separation of photogenerated charge in space is beneficial to inhibit the photogenerated electron-hole recombination.In addition,the introduction of L-phenylalanine regulates the band gap structure of HCPs,which determines the light absorption performance of HCPs and the generation of reactive oxygen species（ROS）.When L-phenylalanine:hexaphenylbenzene was 1:3（H₃LP-HCPs）,it showed the highest photocatalytic activity for the oxidation of amine and the formation of H₂O₂.Detailed mechanism studies show that the excellent photocatalytic performance is due to the interaction of O₂·-and 1O₂.This work provides a new way to design efficient HCPs to promote photocatalytic organic conversion.3.Hollow spherical CeO₂ was synthesized by using PS spherical soft template method,and the hollow spherical heterojunction materials were synthesized by in-situ growth of Znln₂S₄（ZIS）nanosheets on the surface of hollow spherical CeO₂.The constructed Z-type heterostructure greatly improves the separation efficiency of photogenerated electron-hole.The hollow structure provides abundant active sites for the photocatalytic oxidation reaction.A new type of MoS₂-ZIS/CeO₂ heterojunction photocatalyst was synthesized by in-situ photo-deposition of MoS₂ cocatalyst on the surface of ZnIn₂S₄ nanosheets.The Z-type heterojunction acted synergically with non-noble metal MoS₂ cocatalyst.It greatly improves the utilization efficiency of visible light and the separation efficiency of photogenerated electron-hole.Thanks to the excellent light absorption performance of MoS₂-ZIS/CeO₂,the efficient separation efficiency of electrons and holes,and the strong Redox ability,MoS₂ZIS/CeO₂ has excellent photocatalytic activity for the photocatalytic oxidation of benzylamine to produce imine and H₂ reaction under anaerobic condition.