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 ZnIn 2 S 4 with strong Lewis acidity (ZIS) and ZnS with S-vacancy (ZS-Vs) is constructed for activating α -C‒H bond and forming ·O 2 − 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 °C. 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 O 2 activation into ·O 2 − 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. A spatially site-isolated heterojunction (ZnS-Vs/ZnIn 2 S 4 ) is constructed to realize enhanced α -C-H activation for photooxidative upgrading of 5-hydroxymethylfurfural (HMF) to 2,5-furandiformaldehyde (DFF) via the synergistic effect of ligand-to-metal charge transfer (LMCT) and shallow trap states (STS). · A spatially site-isolated heterojunction with S-vacancy/Lewis acidity is constructed. · Photooxidation of HMF to DFF reaches an unprecedented yield of 95.7 % at 25 °C. · Ligand-to-metal charge transfer enables strong Lewis acidity for α-C–H activation. · Shallow trap states by S-vacancy achieve O 2 activation to .O 2 − for C–H bond breaking · The shallow trap states and built-in electric field also accelerate charge separation