High Selective Oxidation of Benzyl Alcohol to Benzylaldehyde and Benzoic Acid with Surface Oxygen Vacancies on W₁₈O₄₉/Holey Ultrathin g-C₃N₄ Nanosheets

Abstract

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 W18O49/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 O2 to O2•– 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).