Boosted Photocatalytic Selective Oxidation of 5-Hydroxymethylfurfural to 2,5-Diformylfuran in Pure Water over Amorphous MoS3-Modified Zn3In2S6 Nanoflowers

The selective photocatalytic oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) into high-value 2,5-diformylfuran (DFF) under green conditions is a promising route toward carbon neutrality. However, achieving high efficiency and selectivity in pure water remains challenging due to limited oxygen solubility and nonselective radical reactions. In this study, a series of amorphous MoS3-modified Zn3In2S6 nanoflowers (x%MS/ZIS) with varying MoS3 loadings were successfully synthesized via a one-step hydrothermal method and served as the photocatalysts for the highly selective oxidation of HMF to DFF. The incorporation of MoS3 significantly enhances visible-light absorption, promotes efficient separation of photogenerated carriers, and accelerates surface reaction kinetics. Under visible light irradiation, the optimized 2.4%MS/ZIS catalyst achieves 64.7% HMF conversion and 89.5% DFF selectivity in pure water within 6 h, ~39-fold enhancement in DFF yield compared to pristine Zn3In2S6. Radical scavenging experiments and electron paramagnetic resonance analyses suggest that superoxide radicals (·O2−) and photogenerated holes are the main reactive oxygen species governing the selective oxidation, while the absence of ·OH radicals suppresses overoxidation. This study demonstrates a viable and green strategy for the valorization of biomass platform molecules through visible-light-driven photocatalysis in pure water.