Magnetic γ-Fe₂O₃@Ir Nanozyme for Molar-Level 5-Hydroxymethylfurfural Oxidation With Atmosphere Oxygen

Direct transformation of biomass-derived platform compound 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) represents a highly attractive route with significant environmental and economic benefits. The nanozymes with oxidase-like (OXD-like) activity hold great promise for the green oxidation of HMF to FDCA. Herein, an iridium-coated γ-Fe₂O₃ core-shell nanozyme (γ-Fe₂O₃@Ir) was prepared by the reduction of Ir³⁺ with glycerol on the surface of γ-Fe₂O_3, and the structure of the γ-Fe₂O₃@Ir nanozyme was confirmed by XRD, HAADF-STEM image, and elemental line-scan analyses results. The magnetic property of the nanozyme not only facilitates its recovery but also effectively enhances its affinity to oxygen. By employing γ-Fe₂O₃@Ir nanozyme as the catalyst and atmospheric oxygen as a green oxidant, a near-quantitative conversion (98.5%) of molar level HMF to FDCA was achieved.