Engineering The Structure Of Bismuth Oxyhalide With Enhanced Visible Light Catalytic Performance For Oxidation Of ?-C-H Bonds In Aromatic Hydrocarbons And Self-coupling Of Benzylamines

Semiconductor heterogeneous photocatalysis technology has been widely used in organic synthesis due to its green and mild reaction conditions and higher selectivity to target products.The two-dimensional bismuth oxyhalide materials exhibit excellent catalytic performance in the fields of photocatalytic water splitting,reduction of carbon dioxide,and degradation of pollutants due to its higher component abundance,nontoxicity,unique layered structure and physical-chemical properties.However,there are relatively few applications in organic synthesis.The previous literature reported that the bismuth oxyhalide materials still have the problems of low quantum eficiency,narrow response range to light,and limited redox ability,which limit its photocatalytic activity to a certain extent.Take into account this,we use structural engineering strategies to regulate the energy band structure of bismuth oxyhalide,improve its visible light catalytic performance,and achieve selective oxidation of hydrocarbon and amines organics.The specific work was as follows:1.BiOBrxI1-x solid solutions were synthesized by a simple hydrothermal method,and used to activate the C-H bond to achieve aerobic selective oxidation of hydrocarbons.The visible light driven photocatalytic activity of benzylic C-H bonds was investigated with N-hydroxysuccinimide at room temperature over BiOBrxI1-x(0?x?1)solid solutions,whose valance bands were engineered through varying the ratio of bromide to iodide.The optimal BiOBr0.85I0.15 catalyst exhibited over 98%conversion of ethylbenzene,which was about 3.9 and 8.9 times than that of pure BiOBr and BiOI samples,respectively.The excellent photocatalytic activity of BiOBr0.85I0.15 solid solution can be ascribed to the orbital hybridization of the valence band containing both Br 4p and I 5p orbitals,which promotes photo-induced carriers separation.Meanwhile,the regulation of the energy band structure of the solid solution can also improve the production of singlet oxygen.The excellent photocatalytic activity of BiOBr0.85I0.15 for the oxidation of ethylbenzene was attributed to the synergistic effect of photo-generated holes and singlet oxygen.In addition,the photocatalytic oxidation of benzylamine and benzyl alcohol was also studied over BiOBrxI1-x solid solution,among which BiOBr0.85I0.15 sample exhibited higher photocatalytic performance.This study exposes that a rational regulation of solid solution photocatalysts can modulate the activation of oxygen in more challenging organic transformation reactions.2.The effect of carbon doping on the selective oxidation of benzylamines by BiOCl photocatalyst was explored.The carbon-doped BiOCl photocatalysts were synthesized by hydrothermal method using glucose as the carbon source and used for selective oxidation of benzylamines.After 1.5 hours of visible light irradiation,benzylamines can be almost completely converted to imines(conversion 99%,selectivity 99%),which was about 11 times than that of pure BiOCl.The excellent photocatalytic activity of carbon-doped BiOCl samples was attributed to the formation of doping energy levels in the original band gap and the enhancement of electric field intensity in the BiOCl lattice,which broaden the visible light absorption range and improve the separation efficiency of photo-generated carriers,respectively.In addition,the doping of carbon makes the BiOCl nanosheets thinner and self-assembles into spherical structure,which increases the specific surface area and exposes more active sites,thereby improving the photocatalytic efficiency of benzylamine.This work shed some light on the rational design of photocatalysts to achieve high-efficiency directional organic conversion.