Surface hydroxyl species enabled Nb2O5 for the photocatalytic oxidation of 5‐hydroxymethylfurfural

Niobium oxide (Nb2O5), an alternative to TiO2, has been recognised as a promising photocatalyst for the oxidation of 5‐hydroxymethyl furfural (HMF) to 2, 5‐diformylfuran (DFF). A series of Nb2O5 photocatalysts are prepared using a simple thermal approach, and their photocatalytic performance for HMF oxidation is tested. Nb2O5 treated at relatively lower temperatures (300‐400 °C) possesses a higher surface area with abundant surface hydroxyl groups and adsorbed water species, which play a key role in the HMF oxidation, affording high DFF selectivity. On the other hand, Nb2O5 treated at higher temperatures (500‐600 °C) exhibits an adverse effect on the photocatalytic performance due to the substantial loss of surface hydroxyl groups and adsorbed water species. Various structural characterisations such as XRD, N2‐sorption analyses and TGA elucidate the changes on the surface of Nb2O5 treated at different temperatures. At the same time, CO2‐TPD, O2‐TPD, and DRIFTS disclose the nature and distribution of active sites, especially strong basic sites, which is essential for comprehending the interaction between HMF and the surface of the catalyst.