Photocatalytic selective oxidation of HMF to DFF based on hollow CdS QDs/MIL-101 composites under visible light

5-hydroxymethylfurfural (HMF) can catalyte into 2,5-diformylfuran (DFF) which had received much attention as a potential biomass resource. Here, we used a simple and effective method to construct hollow CdS quantum dot (CdS QDs)/MIL-101 heterostructures with high contact area and multiple active sites. The structure of heterostructures could improve photocatalytic activity by charge transfer, photogenerated carrier separation and the multiple refractions of light supported within the hollow-structured CdS QDs. The detailed catalytic mechanism was illustrated by trap agent experiments and electron paramagnetic resonance (EPR) spectroscopy, in which superoxide radicals (·O 2 - ) play a decisive role in the catalytic oxidation of HMF to DFF. Furthermore, the large specific surface area of MIL-101 adsorbs O 2 from the reaction system thereby accelerating the ·O 2 - formation process. Under environmental conditions, 70 % CdS QDs/MIL-101 exhibited optimal catalytic performance. Comparing with pure CdS QDs, the photocurrent enhances 1.8 times, HMF conversion is 1.5 times and DFF selectivity is 1.2 times. This work provide a useful way to improve the conversion of biomass by Z-heterostructures under ambient conditions.