Single Cobalt Atoms Induced Molecular O₂ Activation for Enhanced Photocatalytic Biomass Upgrading on ZnIn₂S₄ Nanosheets

Photocatalytic selective biomass aerobic oxidation to high-value products is promising for meeting carbon-neutral demand; however, great challenges remain in the lack of appropriate active sites for molecular O-2 activation and understanding their role at the atomic scale to reveal the underlying mechanism. Herein, we report that a rational decoration of ultralow-amount (0.08 wt %) Co single atoms on ZnIn2S4 nanosheets (Co-1/ZIS) enables both high activity and selectivity for photocatalytic 5-hydroxymethylfurfural (HMF) oxidation to the high-value 2,5-dicarbonylfuran (DFF) product. Under visible light irradiation in an air atmosphere, Co-1/ZIS exhibits 98.6% conversion of HMF that outperforms pristine ZIS by two times, along with 92.4% selectivity of DFF. Uncovered by combined experimental results and computational calculations, the introduction of Co single atoms not only facilitates the transfer of photogenerated carriers but also provides active sites to promote the adsorption/activation of O-2 to generate reactive oxygen species of O-center dot(2)- and O-1(2), thereby leading to its superior photocatalytic performance to the pristine ZIS counterpart.