Visible‑Light‑Driven Selective Oxidation of HMF to FDCA over Fe-Doped g-C3N4 with a Constructed Z-Scheme Heterojunction

Sunlight-driven conversion of biomass into value-added chemicals is crucial for building a sustainable energy future. However, this process often suffers from inefficient light utilization and unclear regulation of reactive oxygen species in photocatalysis. An Fe-doped graphitic carbon nitride (CNFe) photocatalyst was synthesized via a thermal polymerization method and 71.53% conversion of 5-hydroxymethylfurfural (HMF) with 55.56% selectivity to 2,5-furandicarboxylic acid (FDCA) were achieved under visible light. The catalyst was reused for at least four consecutive cycles without significant activity loss, demonstrating good recyclability and stability. Fe doping created a porous sheet-like structure with uniformly embedded Fe 3 O 4 nanocrystals and active Fe-N x sites, which enhanced visible-light absorption and charge separation. The Fe 3 O 4 /g‑C 3 N 4 Z‑scheme heterojunction, synergizing with the redox‑active Fe 3+ /Fe 2+ sites, facilitates efficient O 2 activation to generate selectively superoxide radicals (•O 2 - ). This work demonstrates a feasible strategy for designing efficient non-noble-metal photocatalysts and provides deeper insight into ROS regulation for the sustainable upgrading of biomass-derived feedstocks.