Photocatalytic Cascade Reaction Driven by Directed Charge Transfer over VS‐Zn0.5Cd0.5S/GO for Controllable Benzyl Oxidation

Photocatalysis is an important technique for synthetic transformations. However, little attention has been paid to light‐driven synergistic redox reactions for directed synthesis. Herein, the authors report tunable oxidation of benzyl to phenylcarbinol with the modest yield (47%) in 5 h via singlet oxygen (1O2) and proton‐coupled electron transfer (PCET) over the photocatalyst Zn0.5Cd0.5S (ZCS)/graphene oxide (GO) under exceptionally mild conditions. Theoretical calculations indicate that the presence of S vacancies on the surface of ZCS/GO photocatalyst is crucial for the adsorption and activation of O2, successively generating the superoxide radical (•O2−) and 1O2, attributing to the regulation of local electron density on the surface of ZCS/GO and photogenerated holes (h+). Meanwhile, accelerated transfer of photogenerated electrons (e−) to GO caused by the π–π stacking effect is conducive to the subsequent aldehyde hydrogenation to benzyl alcohol rather than non‐selective oxidation of aldehyde to carboxylic acid. Anisotropic charge transport driven by the built‐in electric field can further promote the separation of e− and h+ for multistep reactions. Promisingly, one‐pot photocatalytic conversion of p‐xylene to 4‐methylbenzyl alcohol is beneficial for reducing the harmful effects of aromatics on human health. Furthermore, this study provides novel insights into the design of photocatalysts for cascade reactions. An approach in controllable benzyl oxidation is provided by photocatalytic synergy of 1O2 and proton‐coupled electron transfer in this work. Surface local electron density impressed by the regulation of S vacancy, as well as π–π interactions between GO and benzene ring facilitate the multistep reactions via separation of photogenerated e− and h+.