Abstract: In response to the problems of poor catalyst performance and numerous reaction by-products in the process of oxidizing 5-hydroxymethylfurfural (HMF) to prepare 2,5-furandicarboxylic acid (FDCA), graphite-like nitrogen-doped carbon (g-C₃N₄) is selected as the support material for the photocatalyst. Different morphologies of g-C₃N₄ support materials are prepared using urea and melamine as precursors, and FeO_x-Au/g-C₃N₄ catalysts with different morphologies are prepared by loading FeO_x-Au onto g-C₃N₄. The structural characteristics of different morphologies of FeO_x-Au/g-C3N4 catalysts and their effects on the performance of the HMF photocatalytic oxidation reaction are characterized. The results show that the nanosheet FeO_x-Au/g-C₃N₄ catalyst prepared using urea as the precursor have the narrowest band gap width, the most excellent ability to absorb visible light, the strongest ability of generating and migrating photo-generated electron-hole pairs onto the catalyst surface, and the strongest ability to produce reactive oxygen species that promote the oxidation of HMF. Under the action of the nanosheetFeO_x-Au/g-C₃N₄ catalyst, the HMF conversion rate reaches 99.9% and the FDCA yield reaches 99.3% after 1 hour of light irradiation at a low HMF concentration (20 mmol/L); at a high HMF concentration (500 mmol/L), the HMF conversion rate is 99.9% and the FDCA yield is 90.2% after 11 hours of light irradiation; superoxide radicals and singlet oxygen are the reactive oxygen species for HMF oxidation, which can promote the oxidation of the aldehyde and hydroxyl groups of HMF molecules.

Key words: 5-hydroxymethylfurfural, 2,5-furanodicarboxylic acid, graphite phase carbon nitride, photocatalytic oxidation