A unique air-assisted DMSO oxidation pathway for the highly efficient synthesis of 2,5-diformylfuran from 5-hydroxymethylfurfural/fructose

The development of safe, economical and highly efficient oxidation systems for the production of chemicals from biomass remains a significant and challenging target. Here, we first found a unique air-assisted reaction mechanism for the non-pressurized oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) using dimethylsulfoxide (DMSO) as an O-donor over CoZrNC-MCM, which affords exceptional productivity among all non-noble catalysts. The combination of control experiments and density functional theory (DFT) calculations reveals that the air-assisted DMSO oxidation pathway is activated by the co-adsorption of DMSO and O₂ on Co-(pyrrolic N-C) pairs of CoNC-MCM. ZrNC species in CoZrNC-MCM will be thermally disintegrated to release ZrO²⁺ and provide the corresponding cation vacancies that might be able to capture Co atoms to form additional Co-(pyrrolic N-C) active pairs, resulting in the increase of catalytic activity. The released ZrO²⁺ is well dispersed over Al-MCM-41 in the form of zirconia, which contributes to the dehydration of fructose to HMF. In this way, a one-step approach for synthesizing DFF from fructose is achieved by the cooperation of zirconia and Co-(pyrrolic N-C) pairs over CoZrNC-MCM.