One-step hydrothermal synthesis of CdxInyS(x+1.5y) for photocatalytic oxidation of biomass-derived 5-hydroxymethylfurfural to 2, 5-diformylfuran under ambient conditions

The CdxInyS(x+1.5y) catalysts with gradient Cd:In ratios were controllably synthesized via an one-step hydrothermal approach. Particularly, the hydrothermal synthesis conferred those CdxInyS(x+1.5y) catalysts with Cd:In ratios over 1:2 with a one-dimensional–three-dimensional heterojunction structure composed of CdS nanorods and cubic-phase CdIn2S4. Our characterization evidences reflected that the CdS nanorods effectively promoted the separation of photoexcited electron–hole pairs in CdxInyS(x+1.5y) and enabled transboundary transfer of photogenerated carriers. Spectroscopic and experimental results were further employed to develop a detailed catalytic mechanism, in which the superoxide anion (•O2−) plays an important role in the catalytic oxidation of HMF to DFF by CdxInyS(x+1.5y). Unlike other photocatalysts with •O2− as the main active species, Cd1.5In2S4.5 gives an excellent performance in HMF conversion. This shows the great potential of cadmium–indium sulfides as photocatalysts for biomass conversion under ambient conditions.