Catalytic Conversion of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid over the Au/Sn–Mg-Beta Catalyst: Synergistic Effect of Lewis Acid–Base Sites

The efficient catalytic conversion of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), a potential renewable polyester monomer, under mild reaction conditions, is a hot topic in biomass valorization. Herein, Sn–Mg–Beta zeolite is hydrothermally synthesized by structural reconstruction, which is used as support to load Au nanoparticle via sol–gel to obtain the Au/Sn–Mg-Beta catalyst. Detailed characterization studies confirm the successful incorporation of Sn and Mg into the zeolite framework and the formation of well-dispersed Au nanoparticles with a diameter of about 6.8 nm. Lewis acid–base pairs exist on the Au/Sn–Mg-Beta catalyst. At 80 °C, it exhibits remarkable performance, achieving nearly complete HMF conversion (99.9%) and an impressive FDCA yield of 97.9%, significantly outperforming Au catalysts supported on single-metal zeolites. Comparative catalytic studies using intermediate oxidation products as substrates and theoretical calculations provide further insights into the reaction mechanism and confirm the crucial role of Mg in facilitating alcohol oxidation and Sn in promoting aldehyde oxidation. This synergistic effect of Lewis acid–base sites within the zeolite support significantly enhances the overall catalytic efficiency. The catalyst also demonstrated good recyclability, highlighting its potential for practical applications. This strategy of incorporating Lewis acid–base pairs within zeolite supports offers a promising route for developing highly efficient catalysts for biomass conversion to valuable chemicals.