Enhanced Selective Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid over Pt–Au/XC Bimetallic Catalysts

The catalytic valorization of biomass-derived 5-hydroxymethylfurfural (HMF) provides an important route toward sustainable chemical production. Herein, we report a bimetallic Pt1Au1 catalyst supported on Vulcan XC-72R carbon (Pt1Au1/XC) that enables efficient aerobic oxidation of HMF to FDCA using NaHCO3 as a weak base. Under optimized conditions (100 °C, 1 MPa O2, NaHCO3/HMF = 3:1, 12 h), the catalyst achieves near-quantitative HMF conversion (>99%) with an FDCA selectivity of 94.2%, substantially outperforming monometallic Pt/XC and Au/XC as well as their physical mixtures. The enhanced performance is associated with the beneficial combination of Pt and Au, together with the favorable surface and transport properties imparted by the carbon support. Kinetic and intermediate-trapping experiments indicate a dual-pathway oxidation mechanism, wherein Au facilitates aldehyde oxidation (via 5-hydroxymethyl-2-furancarboxylic acid (HMFCA)) and Pt promotes alcohol oxidation (via furan-2,5-dicarbaldehyde (DFF)), with both routes converging at 2-formyl-5-furancarboxylic acid (FFCA) for subsequent conversion to FDCA. The catalyst exhibited only a marginal decrease in catalytic activity after five consecutive cycles. Overall, this work provides insight into the roles of bimetallic effects and support properties in HMF oxidation and offers a useful strategy for designing efficient catalysts for biomass-derived furan oxidation.