Efficient photooxidation of C(sp3)-H bonds on visible-light-responsive W-doped TiO2 nanocrystals promoted by photochromic effect

Photocatalytic oxidation of C(sp3)-H bonds using semiconducting catalysts is crucial for value-added chemical production under milder conditions. However, semiconductor-based photocatalysts often suffer from limited active sites and low photoredox activity. Herein, we report W-doped TiO2 nanocrystals that exhibit a photochromic behavior for photocatalytic oxidation of C(sp3)-H bonds with high efficiencies. The photochromic effect induced W5+-Ovs-Ti3+ (oxygen vacancies short as Ovs) active sites in TiO2 nanocrystals act as electron trapping centers to capture and store photogenerated electrons, promoting the photogenerated holes to active C(sp3)-H bonds. Moreover, the Ovs and stored photogenerated electrons on the active sites significantly enhance the adsorption and activation of O2 to O2•-. Owing to the unique photochromic effect, the W-doped TiO2 nanocrystals demonstrate an exceptional photocatalytic production capacity of acetophenone (235 mmol∙g-1), which is 16 times higher than that of pure TiO2 nanocrystals. This work demonstrates the great potential of developing photochromic catalysts for high-efficient ethylbenzene oxidation.