Oxygen Vacancy-Induced Metal-Support Interactions in AuPd/ZrO₂ Catalysts for Boosting 5-Hydroxymethylfurfural...

The construction of strong metal-support interactions in oxide-supported noble metal nanocatalysts has been considered an emerging and efficient way in improving catalytic performance in biomass-upgrading reactions. Herein, a citric acid (CA)-assisted synthesized ZrO₂ layer with improved oxygen vacancy (O_v) concentrations on a natural clay mineral of halloysite nanotubes (HNTs) was designed. Moreover, AuPd/ZrO₂@HNTs-zCA catalysts were prepared by loading AuPd bimetal and employed for aerobic oxidation of the lignocellulosic biomass-derived 5-hydroxymethylfurfural (HMF) platform to the bioplastic monomer 2,5-furandicarboxylic acid (FDCA) with water as the solvent. The results of catalytic experiments revealed that the Au₃Pd₁/ZrO₂@HNTs-1.0CA catalyst exhibited excellent catalytic activity at 0.5 MPa O₂, with a satisfactory FDCA yield of 99.5% and outstanding FDCA formation rate of 1057.9 mmol·g^-1·h^-1. The improved O_v concentration in the ZrO₂ support enhanced the adsorption and activation ability of the catalyst for O₂, and a higher Lewis acid concentration provided a stronger adsorption ability of the catalyst for reaction substrates. Besides, the synergistic effect of AuPd bimetallic nanoparticles steered the tandem oxidation of aldehyde and alcohol groups in HMF and accelerated the rate-determining step. More importantly, the relationship between the O_v concentration and catalytic performance also demonstrated that the enhanced catalytic activity for HMF oxidation was mainly attributed to the active interface of AuPd-ZrO. This work offers fresh insights into rationally designing oxygen vacancy-driven strong interactions between the oxide support and noble nanoparticles for the catalytic upgrade of biomass platform chemicals.