Manipulating and unveiling contributions of the reactive oxygen species dramatically promote selective photo-oxidation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid in aqueous solution

Achieving high selectivity to 2,5-furandicarboxylic acid (FDCA) in the photocatalytic oxidation of 5-hydroxymethylfurfural (HMF) in aqueous solution advocates the principle of green and sustainable chemistry, but still remains a significant challenge. Herein, manipulating the reactive oxygen species (ROS) has been realized and dramatically promotes the selective photocatalytic oxidation of HMF in aqueous solution. High FDCA yield of 98.6% has been achieved after 3 hours of visible light irradiation over the as-prepared FeO_x-Au/TiO₂ catalyst, being one of the leading photocatalytic performances. Furthermore, satisfactory FDCA yields of higher than 80% could be realized even in the outdoor environment under natural sunlight irradiation, regardless of sunny or cloudy weather. A combination study including physical characterization, kinetic analysis, radical trapping experiments and density functional theory calculations unveils the rate-determining step (oxidation of hydroxyl group) and respective contributions of the generated ROS (¹O₂ and·O₂^-) in each step of the entire reaction network. The present work would push ahead the understanding of HMF photocatalytic oxidation and contribute to the rational design of high-performance photocatalysts.