High Selective Oxidation of Benzyl Alcohol to Benzylaldehyde and Benzoic Acid with Surface Oxygen Vacancies on W18O9/Holey Ultrathin g-C3N4 Nanosheets

Synthesis of intermediates and fine chemicals for the selective oxidation of alcohols to corresponding aldehydes and carboxylic acid is an extremely significant chemical reaction. Herein, a binary W18O9/holey ultrathin g-C3N4 nanosheets (HU-CNS) nanocomposite was prepared via a solvothermal method and it exhibited excellent photocatalytic activity for the selective oxidation of benzyl alcohol in an aqueous medium under room temperature and atmospheric pressure. The as-synthesized W18O49/HU-CNS composites showed higher selectivity and conversion efficiency compared to pure g-C3N4, which was mainly ascribed to the moderate adsorption capacity of benzaldehyde on the composite. The high conversion originates primarily from the following: (1) the W18O49/HU-CNS nanocomposite possessing a stronger ability to chemisorb alcohol than g-C3N4; (2) the oxygen vacancies on W18O49 nanowires not only supplied active centers for the activation of O-2 to O-2(center dot-) but also extended the range of light response from the visible to the near-infrared region; (3) the interfacial photogenerated electrons within W18O49/HU-CNS follow a type-II mechanism, which provides a fast transfer route for photogenerated electrons to achieve efficient charge separation. Furthermore, the direct conversion of benzyl alcohol to benzoic acid with high selectivity (>99%) and conversion (>90%) was obtained in the dilute alkaline condition (0.01 M KOH).