Support-driven base-free oxidation of native sugars into the corresponding lactones over gold catalysts: toward bifunctional catalytic materials

Abstract

Base-assisted gold-catalyzed oxidation of carbohydrates into the corresponding esters or lactones is an efficient route to biomass-derived platform molecules, yet the reliance on soluble bases hampers process selectivity and sustainability. Herein, we report a material-centered strategy to suppress the need for external bases in the oxidative transformation of free sugars, by tailoring the chemical nature of the catalyst support. Gold nanoparticles supported on layered double hydroxides (Au/LDH) were synthesized and evaluated as bifunctional catalytic materials for the aerobic oxidation of xylose into 1,4 xylonolactone, a bio-based platform molecule, under mild conditions and compared to Au/Al₂O₃ and Au/MgO. By systematically correlating catalytic performance with the nature of the support, we demonstrate that the metal–support interface plays a decisive role in promoting sugar oxidation while preventing in situ lactone saponification. Using xylose as a representative biomass-derived substrate, a synergistic Au/Al₂O₃–Au/MgO catalytic system enabled quantitative conversion under mild conditions and the selective production of 1,4-xylonolactone in 80% isolated yield. This study reveals that rational design of gold-supported materials offers a powerful route toward base-free oxidation processes and provides transferable insights for the development of advanced catalytic materials for sustainable chemical transformations.