Yb Single-Atom Catalysts for Photocatalytic C–H Activation

Photocatalytic activation of C–H bonds in biomassderived molecules represents a promising strategy for biomass upgrading. However, the efficiency of selective C–H bond activation and oxidation is severely restricted by the sluggish kinetics of photogenerated carriers and the uncontrollable generation of reactive oxygen species. Herein, we delicately dispersed Yb single atoms on ZnIn2S4 nanosheets that boost the photocatalytic directional activation of C–H in 5-hydroxymethylfurfural (HMF). The optimized Yb0.8-ZIS achieves a balance between 2,5-diformylfuran selectivity (99.8%) and production rate (906.6 μmol g–1 h–1 ) under ambient conditions. Mechanistic studies reveal that Yb single atoms not only effectively modulate the electronic structure of ZnIn2S4 but also serve as hole extractors, thereby enhancing the separation of photogenerated carriers and the activation of oxygen. Furthermore, the ligand-to-metal charge transfer between Lewis acidic Yb sites and HMF effectively reduces the electron density of the α-C–H bond, thus accelerating the activation process. This work offers insight into the rational design of rare-earth single atoms for modulating both charge dynamics and molecular activation in selective C–H activation and oxidation. KEYWORDS: Yb single-atom, C–H activation, electronic structure, photocatalytic oxidation, 5-hydroxymethylfurfural