Fe-N Coordination Tunes Lattice Oxygen Mobility in Fe@CN for Selective Oxidation of Crude 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid

Owing to the scarcity of natural resources, the polyester industries have turned to synthesizing 2,5-Furandicarboxylic acid (FDCA) from 5-hydroxymethylfurfural (HMF) to replace terephthalic acid for meeting their extensive demands. Achieving efficient oxidation of cheap and available crude-HMF into FDCA presents significant challenges. Herein, a highly dispersed Fe₃N nanoparticle catalyst anchored on N-doped carbon (Fe@CN) was developed for efficient aerobic oxidation of crude HMF to FDCA, a key renewable alternative to terephthalic acid. The Fe@CN catalyst delivers a 94% FDCA yield with exceptional stability under 150 °C, 3 MPa air, 3 h in aqueous solution, outperforming most non-noble metal catalysts. Structural and mechanistic studies reveal that Fe-N coordination weakens Fe-O bonds and boosts lattice oxygen mobility, accelerating the rate-determining hydroxyl oxidation step via a Mars-van Krevelen mechanism. Preferential adsorption of the HMF hydroxyl group on Lewis acidic Fe³⁺ sites direct the dominant pathway through 2,5-diformylfuran (DFF). Dynamic Fe²⁺/Fe³⁺ redox cycling and efficient lattice oxygen replenishment at pyridinic-N sites sustain catalytic activity. This work offers a general design principle for low-cost, robust catalysts toward sustainable biomass valorization.