Novel application of g-C3N4/NaNbO3 composite for photocatalytic selective oxidation of biomass-derived HMF to FFCA under visible light irradiation

The g-C₃N₄/NaNbO₃ photocatalyst was synthesized by simply calcining the mixture of NaNbO₃ and melamine. The synthesized composite exhibits high photocatalytic performance in the selective oxidation of 5-Hydroxymethylfurfural (HMF) to 5-formyl-2-furancarboxylic acid (FFCA) when using water as solvent. The structure and composition of g-C₃N₄/NaNbO₃ photocatalysts were characterized by TG, XRD, SEM, UV–Vis, FT-IR, and XPS methods, and the optical and electrochemical properties were investigated by EIS, PC, and PL techniques. O₂^? was inferred to be the primary active species in this process based on the active species trapping experiment. Heterostructure formation of g-C₃N₄/NaNbO₃ composites efficiently promoted the separation of photo-generated electron-hole pairs and accelerated the electron transfer rate, thus reduced the formation of OH, and sequentially improved the selectivity of FFCA. The highest HMF conversion of 35.8% with FFCA selectivity of 87.4% was achieved on C/N-59.6 photocatalyst under the irradiation of visible light. The possible mechanism and reaction route were also proposed.