Boosting Photocatalytic Selective Oxidation of 5-Hydroxymethylfurfural to 2,5-Diformylfuran via Atomically Bridged Indium in In-SnS.

The photocatalytic conversion of biomass-based platform molecules, such as 5-hydroxymethylfurfural (HMF), holds significant importance for the utilization of biomass resources. This study focuses on the unique ability of atomically bridged indium (In) atoms that encourages inactive SnS surface and steer the selective HMF oxidation process under solar light. Experimental results suggest that In confined SnS structure provides not only favorable sites and electronic structures for the synergistic activation of HMF/O but also benefit in charge carrier dynamics, thus influencing the overall activity and selectivity of the SnS catalyst. In addition, in-situ spectroscopy and density functional theory (DFT) analysis uncovered the multifunctional role of In sites in promoting the key steps of the catalytic process, from reactive oxygen species (ROS) generation to regulated adsorption/activation of *HMF which serves as the rate limiting step of the overall HMF oxidation process. Consequently, the optimized In-SnS-0.75 photocatalyst demonstrated excellent photo oxidation performance, reaching a high HMF conversion efficiency, yield, and selectivity of 91.2, 73 and 80 % respectively, in just two hours of the reaction. This study highlights the strategic approach of rationally designed catalytic systems in order to tune the ROS and the product distribution of the HMF oxidation process.