Catalytic oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran using MOF-808(Cu) under near ambient conditions

Abstract

Biomass conversion involves transforming sustainable feedstocks into valuable intermediates for the chemical industry. A key biomass-derived platform molecule, 5-hydroxymethylfurfural (HMF), can be converted into various intermediates, including 2,5-diformylfuran (DFF), which has several industrial applications due to its versatile chemical reactivity. Herein, Cu loaded MOF-808, with three different Cu loadings, were synthesised and tested as catalysts for the liquid phase selective oxidation of HMF to DFF with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO). X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) were performed to assess the speciation of Cu, with the development of a structure model of MOF-808(Cu₃). The structural analysis reveals that single square planar Cu(II) sites are located near the Zr₆ cluster and are bonded by coordinating to oxygen atoms of capping MeOH and H₂O ligands. Amongst the synthesised catalysts, MOF-808(Cu₃) exhibited the highest catalytic activity after 12 h, achieving a high HMF conversion (95.5 ± 2.7%) and DFF yield (78.9 ± 1.3%) at 30 °C. The nature of the catalytic reaction is heterogeneous as the yield of DFF decreases after the removal of the solid catalyst. The demonstration of catalytic activity with high selectivity under near ambient conditions advances the application of porous metal–organic framework-based catalysts for selective liquid phase oxidations.