Well-Arranged Hollow Au@Zn/Ni-MOF-2-NH₂ Core–Shell Nanocatalyst with Enhanced Catalytic Activity for Biomass-Derived <scp>d</scp>-Xylose Oxidation

Abstract

Highly base-free catalytic of biomass-derived feedstock into value-added chemical is of great interest in catalysis but remains a challenge. Herein, a hollow nanocatalyst composed of Au nanoparticles as the core and Zn/Ni bimetallic metal–organic frameworks (MOFs) functionalized with the −NH2 ligand as the shell (Au@Zn/Ni-MOF-2-NH2) is fabricated through a straightforward one-pot hydrothermal method for a highly efficient, selective, and base-free synthesis of d-xylonic acid by the catalytic oxidation of d-xylose. Experimental and theoretical results confirmed the key role of hollow core–shell Au@Zn/Ni-MOF-2-NH2 in providing in-depth synergistic effects between the Au nanoparticles and the porous MOF and further facilitating the transport of reactant and product molecules, triggering a noticeably impressive turnover frequency value of 76.53 h–1 for d-xylonic acid generation, outperforming the bare Au nanocatalyst by 306 times. The highly integrated structure of Au@Zn/Ni-MOF-2-NH2 is stable for recycled use during the oxidation process, which further demonstrates the superior availability of such a bimetallic MOF-based hollow core–shell heterogeneous nanocatalyst.