Harnessing earth-abundant clay mineral for sustainable catalysis: Electronic tailoring of AuPd bimetallics enables efficient alkali-free 5-hydroxymethylfurfural upgrading

Production of high value-added 2,5-furandicarboxylic acid (FDCA) from 5-hydroxymethylfurfural (HMF) is a promising alternative to petroleum derivate of terephthalic acid. However, it is still challenging to construct efficient and easily available catalysts suitable for green production process of FDCA under base-free conditions. Herein, a natural clay mineral sepiolite supported AuPd bimetallic catalysts with varied bimetallic ratio were developed and employed for aerobic oxidation of HMF to produce FDCA under alkali-free hydrothermal conditions. Au_1.2Pd₁/sepiolite catalyst showed the best catalytic performance with 100% HMF conversion and 98.4% FDCA yield. The key to excellent catalytic performance benefited from synergistic effect between hydroxy-rich surface property of natural sepiolite support and the positive role of AuPd bimetallic sites in the tandem oxidation of aldehyde and hydroxyl groups. The localized electron transfer between AuPd nanoparticles and carriers was investigated by density functional theory calculations. The bimetal promoted the formation of electron-rich interfaces, modulated the local electron redistribution at the interface, and enhanced the adsorption and activation of O₂, HMF, and the reacted formed intermediates. This work presents a promising strategy for green synthesis of FDCA as well as offers a facile way for the high-value usage of nanofibrous clay mineral.