Cooperative α-C–H activation enabled quantitative and partial photooxidation of biomass-derived 5-hydroxymethylfurfural

Photocatalytic activation of C-H bonds is versatile but challenging for undergoing oriented conversion processes. Herein, a spatially site-isolated heterojunction (ZS-Vs/ZIS) of ZnIn₂S₄ with strong Lewis acidity (ZIS) and ZnS with S-vacancy (ZS-Vs) is constructed for activating α-C-H bond and forming ·O₂^- to cleave the C-H bond, respectively. ZS-Vs/ZIS displays outstanding performance in visible-light partial photooxidation of bio-based 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) in an unprecedented yield of 95.7% at 25 ºC. In-situ experiments and calculations reveal that Zn sites of ZIS serve as hole enrichment to adsorb HMF for α-C-H activation via ligand-to-metal charge transfer. Shallow trap states introduced by S-vacancy in ZS-Vs act as an electron pool to realize directed O₂ activation into ·O₂^- for breaking pre-activated α-C-H bond in HMF to exclusively give DFF. Moreover, ZS-Vs/ZIS has good recyclability and universality in the photooxidation of various alcohols to carbonyls (86.4-95.6% yields). The synergistic C-H activation/breaking strategy exhibits high potential in targeted photocatalytic transformations.