Visible-Light-Driven Oxidation of Benzene to Phenol with O over Photoinduced Oxygen-Vacancy-Rich WO.

Direct photocatalytic conversion of benzene to phenol with molecular oxygen (O) is a green alternative to the traditional synthesis. The key is to find an effective photocatalyst to do the trick. Defect engineering of semiconductors with oxygen vacancies (OVs) is an emerging strategy for catalyst fabrication. OVs can trap electrons to promote charge separation and serving as adsorption sites for O activation. However, the randomly distribution of OVs on the semiconductor surface often results in mismatching the charge carrier dynamics under irradiation, thus failing to fulfill the unique advantages of OVs for photoredox functions. Herein, we demonstrate that abundant OVs can be facilely generated and precisely located adjacent to the reductive sites on reducible oxide semiconductors such as tungsten oxide (WO) via a simple photochemistry strategy. Such photoinduced OVs are well suited for photocatalytic benzene oxidation with O as they readily capture photogenerated electrons from the reductive sites of WO to activate adsorbed O. The oxygen-isotope-labeling experiments further confirm that the OVs also facilitate the integration of oxygen atoms from O into phenol, revealing in detail the pathway for photocatalytic benzene hydroxylation. This study demonstrates that the photochemistry approach is an appealing strategy for the synthesis of high-performance OVs-rich photocatalysts for solar-induced chemical conversion.