Abstract
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 ((1) O(2) ) and proton-coupled electron transfer (PCET) over the photocatalyst Zn(0.5) Cd(0.5) S (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 O(2) , successively generating the superoxide radical ((•) O(2) (-) ) and (1) O(2) , 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.