Construction And Application Of Photo Enzyme Integrated Catalyst Based On Hollow TO₂

Compared with traditional single catalyst,the synergy of different catalytic reaction can be realized in the same system through the integrated catalyst.The transfer of reaction substrate among the activity sites of different catalyst can both improve the catalytic performance and achieve the reaction that can not be proceeded or completed by a single catalyst.Photo-enzyme integrated catalysts combine the photocatalytic ability of semiconductors with the catalytic ability of biological enzymes which have high efficiency and unique regio/stereospecificity under mild reaction conditions thus achieving the integration of two green and sustainable catalytic technologies.The construction of integrated catalyst can effectively overcome the disadvantages of free enzymes,such as difficult recovery,poor stability,and high cost,and tap the potential of photocatalysis,thus becoming a promising multipurpose green chemical manufacturing platform.In this thesis,we designed and prepared photocatalysts with strong photocatalytic performance and good biocompatibility to immobilize enzymes,which combined photocatalysis of semiconductor and biocatalysis of enzyme to construct photo-enzyme integrated catalysts.Then we studied the structure-activity relationship between different catalytic methods and active sites,and application of integrated catalysts in organic pollutant degradation and chiral chemical synthesis.The specific research content is as follows:（1）Hollow structure titanium dioxide（H-TiO₂）was prepared using dendritic mesoporous silica nanoflowers（DMSNs）as hard template.Cu-H-TiO₂microspheres with uniform morphology and obvious hollow structure were obtained by loading metal copper,and they were used to immobilize laccase.The activity of immobilized laccase（Lac@Cu-H-TiO₂）was 17.4 U/mg_supportand the enzyme activity recovery was 65.7%at the concentration of 0.05 mg/m L,p H 5.0 and 25℃with the adsorption time of 60 min.The immobilized enzyme was used for photo-enzyme synergistic degradation of 2,4-dichlorophenol under visible light.Under the conditions of p H 5.0,xenon light 300W and initial concentration 10 mg/L,the degradation rate of Lac@Cu-H-TiO₂was 95.2%after 12h,which was higher than that of single photocatalysis（61.7%）and enzyme（69.1%）.And the intergrated catalyst had good reusability（residual activity of 80.5%after 10 cycles）.The stability of immobilized enzyme was also significantly improved.Compared with the degradation effect of different catalysts on phenol organic phenol,bisphenol A,4-chlorophenol and p-nitrophenol（10 mg/L）,Lac@Cu-H-TiO₂had the highest degradation rate in visible light,which were 91.8%98.0%92.9%and 89.4%,respectively.The results show that the photo-enzyme integrated catalyst for immobilized laccase has a broad application prospect in the degradation of organic pollutants.（2）Using magnetic dendritic mesoporous silica nanoflowers as hard templates,superparamagnetic yolk shell Fe₃O₄@H-TiO₂/Cu was constructed by loading TiO₂and Cu,and it was used to immobilize chloroperoxidase（CPO）.Under the conditions of p H 3.0,initial enzyme concentration 0.72μM and 25℃for 40 min,the maximum activity of the immobilized enzyme was 21.8 U/mg_support,and the enzyme activity recovery was 66.1%.Moreover,the immobilized enzyme showed better p H,thermal and photoradiation stability than the free enzyme.Under visible light irradiation,CPO@Fe₃O₄@H-TiO₂/Cu realized in situ,continuous and controllable H₂O₂supply and activated CPO activity,converting methyl phenyl sulfide to R-methyl phenylsulfoxide with final yield of 95.4%and ee value of 99.9%.After 10 cycles,the yield reached 56.5%and the ee value maintained at 99.9%.The results show that photo-enzyme integrated catalyst for immobilized CPO has a good application prospect in chiral synthesis.