Construction Of Heterogeneous Biomimetic Catalyst Based On β-cyclodextrin And Their Application

β-Cyclodextrin has the special structure and nature with "internal cavity hydrophobic and outer wall hydrophilic",and it is easy to be renewable.According to the characteristics of their abundant hydroxyl functional groups,the modified β-cyclodextrin can be immobilized on the active carrier and used to catalyze the asymmetric oxidation of benzyl sulfide.Fe3O4 nanoparticles were prepared by combining FeCl3·6H2O and FeCl2·4H2O under basic conditions.The Si@Fe3O4 carrier with the core-shell structure was prepared by combining 3-chloropropyltriethoxysilane and ethyl orthosilicate with Fe3O4 nanoparticles.In order to investigate the activity of β-cyclodextrin immobilized on the carrier,the β-cyclodextrin matrix was immobilized onto Si@Fe3O4 carrier by using ethylenediamine as the linking group,and it was used to adsorption the pnitrophenol to examine its properties.The results of FT-IR,XPS,XRD,TGA,SEM,TEM and Water contact angle showed that the preparation of the carrier and the process of cyclodextrin immobilization have been successful.The effects of pH value,adsorption time and adsorption temperature on the adsorption capacity of pnitrophenol were investigated.The results showed that the time to reach the adsorption equilibrium was 15 s,and the saturated adsorption capacity reached 84.2 mg/g when the pH value is 7.0.It is proved that the Si@Fe3O4 carrier has excellent properties.Based on this and Cl@Si carrier which was previously studied,the heterogeneity of cyclodextrin was achieved.In this experiment,6-ethanolamine-β-cyclodextrin and 6-propanolamine-β-cyclodextrin were synthesized by using ethanolamine and propanolamine as the modifying group.Then 1-chloro-3-iodo-propane was used as the linker.The two β-cyclodextrin derivatives were successfully immobilized on the two carriers,and then complexed with Na2MoO4 to construct β-cyclodextrin nonhomogeneous catalyst.The preparation of the heterogeneous bionic catalyst ligand was confirmed by FT-IR,XPS,XRD,TGA,SEM,TEM and Water contact angle analysis.And the performance of the biomimetic catalyst for the asymmetric oxidation of benzyl sulfide was investigated.The results showed that the introduction of the carrier did not affect the asymmetric oxidation reaction of cyclodextrin derivatives to benzyl sulfide,the substrate conversion rate was 100.0%,the yield of the product was 83.4% and the ee% value reached 55.3%.Experiments not only use the green solvent instead of organic solvents,and the catalyst can be recycled,meeting the "green chemistry" concept.In the process of screening the catalytic activity center,we found that protonic acid is a kind of excellent catalyst.In order to study the catalytic performance and the principle of the oxidation of protic acid to benzethonium thioether,we systematically investigated the catalytic performance of that a series of protonic acids catalyzed H2O2 to oxidation sulfide,and we revealed the common problem.The results showed that the catalytic activity of all the proton acids is related to the pH value of the reaction system.As long as the pH value of the reaction system reaches about 1.30,all the protonic acid catalysts can make the reaction conversion and yield reach about 98.0% even above.We first proposed that the catalytic activity is determined by the pH value of the reaction system in the proton acid catalytic oxidation of sulfide system.