Highly Selective Photocatalytic Conversion of 5‐Hydroxymethyl‐2‐furfural to 2,5‐Diformylfuran over Gold Ion Exchanged Cadmium Sulfide Nanowire

Abstract 5‐Hydroxymethyl furfural (HMF) obtained from biomass can be converted to 2,5‐diformylfuran (DFF), a valuable chemical intermediate. However, the typical HMF oxidation process requires energy consumption such as high temperature and oxygen pressure. Herein, Au₂S decorated CdS nanowires (denoted as Au₂S@CdS NWs) are fabricated by a simple ion exchange method and applied as a heterostructure photocatalyst system for HMF oxidation under mild conditions. Under visible light irradiation, the photocatalytic performance of Au₂S@CdS NWs is significantly enhanced compared with pristine CdS NWs, in which Au₂S (0.25%)@CdS NWs achieve the high DFF yield (≈95%) for 4 h reaction time. This result means that the heterogeneous interface formed between CdS NWs and Au₂S promotes the separation efficiency of photogenerated charges, which leads to high catalytic activity. Moreover, Au₂S (0.25%)@CdS NWs work well for HMF conversion to DFF under anaerobic and aerobic conditions. Control experiments and characterization are conducted to investigate each reaction mechanism. Consequently, it is found that the photogenerated hole directly oxidizes HMF to DFF under anaerobic conditions and the ¹O₂ produced from oxygen is the active species for HMF conversion to DFF under aerobic conditions.