MnCo2S4/SnIn3S6.5 S-Scheme Heterojunction for selective photocatalytic oxidation of 5-Hydroxymethylfurfural to 2, 5-diformylfuran in water

Abstract

Solar-driven photocatalytic conversion of 5‑hydroxymethylfurfural (HMF) represents a crucial route for renewable resources utilization. However, current photocatalysts generally suffer from poor product selectivity. Herein, we construct an MnCo2S4/SnIn3S6.5 (MCS/SIS3) S‑scheme heterojunction for the selective oxidation of HMF to 2,5‑diformylfuran (DFF) in water. The S‑scheme charge transfer pathway not only suppresses carrier recombination via the built‑in electric field, but also preserves the strong reducing and oxidizing capabilities of the charge carriers. Moreover, the heterojunction weakens the hydrogen‑bonding network of interfacial water on the catalyst surface, which increases the diffusion coefficient of HMF and thus accelerates substrate mass transfer. The synergistic effect of these two factors endows 3%MCS/SIS3 improved photocatalytic activity. Under blue‑light irradiation, the optimal 3%MCS/SIS3 composite achieves an HMF conversion of 85.6% and a DFF selectivity of 90.4% within 3hours. Photogenerated holes and singlet oxygen are identified as the primary reactive species. Holes directly drive the bond cleavage of the hydroxymethyl group to form aldehyde group, while singlet oxygen acts as a proton acceptor. This work reports the application of an MnCo2S4‑based S‑scheme heterojunction in photocatalytic biomass conversion, offering a new avenue for the selective production of DFF under green aqueous conditions.