The Preparation Of Thiophene-conjugated Porous C₃N₄ Nanosheets And The Construction Of Artificial Photo-biocatalytic Hybrid System

Photo-biocatalytic hybrid system as an appealing platform for solar-to-chemical conversion of value-added chemicals and biofuels has received widespread attention.The synergy between the enormously enhanced photocatalytic redox cofactor regeneration system with the remarkable stereoselectivity and specificity of oxidoreductases could enable prominent catalytic conversion efficiency in solar-to-chemicals production.However,a critical bottleneck limiting the performance of the photo-biocatalytic hybrid system is the low efficiency of photocatalytic regeneration of redox-active cofactors,a vital step in coupling photocatalysis and biocatalytic transformations.Many photocatalyst materials such as organic dyes,inorganic semiconductors,transition-metal complexes,and polyoxometalates have been explored for redox-active cofactors recycle to reduce the high cost of these cofactors in redox enzymatic reactions.However,the toxicity of heavy metals,poor chemical stability and the phototoxicity to enzymes of these materials are unfavorable for photo-biocatalytic hybrid systems.In this study,we synthesized thiophene-conjugated porous C₃N₄nanosheets(CN-ATCN)with conjugation of thiophene groups into the carbon nitride framework,which exhibited prominently boosted photo-regeneration activity of nicotinamide cofactors(NADH and NADPH).The catalytic turnover frequencies(TOFs)of NADH and NADPH are 14.09 h^-1and 9.79 h^-1,respectively,which,to the best of our knowledge,are the highest efficiency in NAD(P)H regeneration reported to date.The nanosheet structure facilitates exposure of active sites to reactants and favours the diffusion of reactants and products,which are benifical for photocatalysis.Upon conjugation of carbon nitride framework with thiophene moiety,the extended?-conjugation system in frameworks leads to the decrease of bandgap by 0.52 e V and effectively improves the light absorption property of CN-ATCN.Moreover,molecular type II heterojunctions are constructed between the incorporated and non-incorporated portions of CN-ATCN,intrinsically enhancing the separation of photo-excited electron-hole pairs,thus enormously improve the performance of photo-regeneration of NAD(P)H.CN-ATCN was then applied in the NAD(P)H-dependent photo-enzymatic hybrid systems for the sustainable synthesis of styrene oxide and L-tert-leucine(two key intermediates for chemical and pharmaceutical industry),and exhibited 2.1-and 2.8-folds enhancement in the solar-to-chemical conversion activity,respectively,in comparison to those of the bulk g-C₃N₄counterparts.This work could provoke further development of highly efficient photo-biocatalytic hybrid systems to promote solar-to-chemical conversions.