Recent Advances in Liquid-phase Heterogeneous Photocatalysis for Organic Synthesis by Selective Oxidation

Selective oxidation of organic compounds in liquid-phase heterogeneous photocatalysis is crucially important, and the promising reaction routes attracted great attention in the past few years. Many novel systems were designed to obtain high selectivity for organic synthesis and the mechanism was proposed. This paper reviews the recent developments of liquid-phase heterogeneous photocatalysis for organic synthesis by selective oxidation under ultraviolet or visible light. Alcohol oxidations, aromatic hydroxylations, alkene oxidations, cyclohexane oxidations and C-C coupling reactions are discussed by using various semiconductors, such as TiO2-based photocatalysts, ZnIn2S4, RGO-Ag3VO4, Bi2O3/TiO2-xNx, Fe/Al/silicate and Au/ZnO. In particular, benzyl alcohol and its derivatives to aldehydes, C-C coupling reactions to 2,3-butanediol and aliphatic pinacol, benzene to phenol, phenol to benzenediol, and cyclohexane to cyclohexanol or cyclohexanone were reviewed in details. The photooxidation processes discussed were carried out in aerobic or anaerobic condition, and the photocatalysis factors, such as the reaction condition, the solvent, and the structure of photocatalyst, played a key role in controlling the selective oxidation of organic compounds.