High Selective Oxidation of Benzyl Alcohol to Benzylaldehyde and Benzoic Acid with Surface Oxygen Vacancies on W18O49/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 W 18 O 49 /holey ultrathin g-C 3 N 4 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 W 18 O 49 /HU-CNS composites showed higher selectivity and conversion efficiency compared to pure g-C 3 N 4, which was mainly ascribed to the moderate adsorption capacity of benzaldehyde on the composite. The high conversion originates primarily from the following: (1) the W 18 O 49 /HU-CNS nanocomposite possessing a stronger ability to chemisorb alcohol than g-C 3 N 4; (2) the oxygen vacancies on W 18 O 49 nanowires not only supplied active centers for the activation of O 2 to O 2 •– but also extended the range of light response from the visible to the near-infrared region; (3) the interfacial photogenerated electrons within W 18 O 49 /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).