Solar energy-driven processes for biomass valorization are priority for the growing industrialized society. To address this challenge, efficient visible light-active photocatalyst for the selective oxidation of biomass-derived platform chemical is highly desirable. Herein, selective oxidation of 5‑hydroxymethylfurfural (HMF) to 2,5- diformylfuran (DFF) is achieved by visible light-driven photocatalysis over titania. Pristine titania is photocatalytically inactive under visible light, an unconventional approach is employed for the visible light (λ =515 nm) sensitization of titania via a formation of a visible light absorbing complex of HMF (substrate) on the titania surface. Surface-complexation of HMF on titania mediate ligand-to-metal charge transfer (LMCT) under visible light, which efficiently catalyzes the oxidation of HMF to DFF. A high DFF selectivity of 87% is achieved with 59% HMF conversion after 4 hours of illumination. Whereas, the apparent quantum yield obtained for DFF production is calculated to be 6.3%. It is proposed that the dissociative interaction of hydroxyl groups of HMF and the titania surface is responsible for the surface-complex formation. When the hydroxyl groups of titania are modified via surface-fluorination or calcination the oxidation of HMF is inhibited under visible light, signifying that hydroxyl groups are decisive for photocatalytic activity.
A. Khan, M. Goepel, A. Kubas, D. Łomot, W. Lisowski, D. Lisovytskiy, A. Nowicka, J.C. Colmenares, and R. Gläser. ChemSusChem, 14 (2021) 1351 –1362. OPEN ACCESS!!!
http://dx.doi.org/10.1002/cssc.202002687
Sign-up for our science Newsletter