Visible Light Catalytic Oxidation Of Alkanes C-H Bonds And Organic Amine N-H Bonds

The development of new catalytic processes and catalytic materials has always been an important driving force for the development of catalytic science.The selective oxidation of C-H bond of alkanes and N-H bond of organic amines involved high temperature activation of reactants,however,the selectivity of products is limited by thermodynamics.Recently,the development of visible-light-driven selective catalytic oxidation as a more environmentally friendly method has become a new direction of industrial organic synthesis.KA oil（cyclohexanone and cyclohexanol）and N-benzylidene benzylamine（imine）are important organic chemical intermediates,which are widely used in the fields of medicine and materials.In this paper,the photocatalytic oxidation of cyclohexane and organic amines on titanium silicalite molecular sieve and biomass carbon materials were studied,which provided a new method for the development of efficient visible light photocatalysts.（1）Selective photocatalytic oxidation of cyclohexane to KA oil was carried out by using hollow titanium-silicalite（HTS-1）loaded with different metal chlorides as photocatalysts and molecular oxygen as green oxidant.The results showed that HTS-1 modified by CuCl₂ was the best photocatalyst for this reaction.The conversion of cyclohexane is 23.5%and the selectivity of KA oil is 99%in acetonitrile after 4 h.Substrate exploration experiments of different alkanes showed that the catalyst has good universality.XRD,N₂ adsorption-desorption and TEM analysis showed that CuCl₂ was highly dispersed on the surface of the hollow molecular sieve.FT-IR,UV-vis DRS and XPS characterization confirmed that CuCl₂ species were bonded through Cu-O-Ti bridge.Theoretical calculation and simulation calculation showed that CuCl₂ changed the low unoccupied molecular orbital（LUMO）of the photocatalyst,and the main contribution is the hybrid state composition of Cu²⁺3d,Cl^-2p,O^2-2p and Ti⁴⁺3d.Combined with the radical trapping experiments,a possible oxidation mechanism for the formation of Cl·and·OH radicals from photogenerated electrons and holes was proposed.（2）Biomass carbon photocatalysts with high photocatalytic activity were prepared by hydrothermal synthesis from different biomass raw materials.Benzylamines were selectively oxidized to imines by molecular oxygen.Bamboo powder-based carbon material was used as photocatalyst,and the conversion of benzylamine was 95%and the selectivity of imine was 99%after irradiation for 32 h.Substrate exploration experiments of different alkanes showed that the substrate with activeα-H can be smoothly converted into the corresponding imine product,and there are obviously existence of electronic effects and steric effects.The characterization of FT-IR,Raman,XRD,TEM and N₂ adsorption showed that the hydrothermal carbonization temperature affected the construction of active sites on the surface of the biomass-derived carbon photocatalyst.Combined with organic small molecule catalyst exploration experiments,it was proved that the phenolic structure and quinone structure on the surface of photocatalyst were the main active sites of photocatalysis.