Oxygen Vacancy-Enhanced Selectivity in Aerobic Oxidation of Benzene to Phenol over TiO2 Photocatalysts.

Photocatalytic oxidation of benzene to phenol using molecular oxygen (O2) is a promising alternative to the traditional cumene process. However, the selectivity toward phenol is often poor due to the ring-opening reaction induced by the superoxide radical (⋅O2 -), which is predominantly produced from the single-electron reduction of O2. Herein, we demonstrate that introducing abundant oxygen vacancies (OVs) on the surface of titanium dioxide (TiO2) facilitates the activation of O2 through a two-electron reduction process instead of a single-electron reduction. This effectively suppresses the generation of ⋅O2 -, thereby reducing phenol decomposition and significantly enhancing the selectivity. In addition, these OVs can trap the electrons to promote chare separation and serve as the adsorption sites for O2 activation. As a result, the introduction of abundant OVs on the surface of TiO2 not only enhances phenol yield but also importantly improves selectivity toward phenol. This finding enriches our understanding of how OVs influence reaction pathways and product selectivity, providing valuable insights for the design and tailoring of OV-rich photocatalysts for selective organic oxygenations.