Research on highly efficient photocatalytic selective oxidation of HMF to DFF using CdS@MXene Composites: Construction of Schottky junctions and mechanistic investigation

Abstract

Highly-effective photocatalytic selective oxidative valorization of renewable 5-hydroxymethylfurfural (HMF) into 2,5-diformylfuran (DFF), a biomass-derived platform chemical, remains a challenging task for chemists. In this work, uniformly distributed CdS nanospheres were synthesized using the deep eutectic solvent method and subsequently loaded onto monolayer MXene nanosheets. This method successfully yielded CdS@MXene Schottky junction photocatalysts. The outstanding electron-trapping capability of MXene significantly improves the selectivity and long-term stability of CdS@MXene, which is capable of being used for photocatalysis DFF production from HMF. Up to 91.63 % of DFF selectivity can be obtained from 1 mM of HMF by CdS@MXene-11 % under visible light irradiation using water as solvent. Density functional theory was further adopted to investigate electron transfer between CdS and MXene, confirming the presence of a Schottky junction for the enhanced separation and interfacial transfer efficiency of photogenerated carriers. The mechanism for the photocatalysis production of DFF from HMF was proposed by employing electron paramagnetic resonance, which suggests ·O2– as the main radical, and plays a decisive role in the selective oxidation process. This work provides new insights into construction of MXene-based Schottky junction as a promising approach for the photocatalytic valorization of biomass under mild conditions.