Bidirectional S-bridge coordination in the magnetic Au/FeOxSy catalyst for the catalytic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid

Abstract

The aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is a promising approach for producing renewable biodegradable plastics. However, thus far, the development of catalytic oxidation processes operating under mild conditions and the design of highly stable catalysts have been challenging. Herein, the magnetic catalyst Au/FeO_xS_y was synthesised by doping S into the Fe/Au bimetallic structure. The reaction was conducted in water at 60 °C under air and atmospheric pressure, achieving 100% conversion of HMF and a FDCA yield of 98.5%. The catalytic performance of S-doping Au/FeO_x was 4.73 times greater than that of undoped Au/FeO_x under the same conditions. Furthermore, the catalyst demonstrated excellent cycling stability, with the FDCA yield maintained above 93% after at least 30 cycles. The introduction of S altered the electronic configuration of Au through the formation of Au–S bonds, thereby enhancing electron mobility and catalytic activity. Additionally, the interaction of S with FeO_x led to the formation of Fe–O–S bonds, which fortified the structure of the catalyst and ensured prolonged cycling stability. Thus, this study effectively converted HMF to FDCA under mild conditions through S incorporation, offering a novel approach for preparing metal catalysts and laying a robust foundation for utilising FDCA as a sustainable alternative to terephthalic acid in bio-based polyester production.