Theoretical study on molecular mechanism of aerobic oxidation of 5-hydroxymethylfurfural to 2,5-diformyfuran catalyzed by VO with counterpart anion in ,-dimethylacetamide solution.

Vanadium-containing catalysts exhibit good catalytic activity toward the aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformyfuran (DFF). The aerobic oxidation mechanism of HMF to DFF catalyzed by VO with counterpart anion in ,-dimethylacetamide (DMA) solution have been theoretically investigated. In DMA solution, the stable VO -containing complex is the four-coordinated [V(O)(DMA)] species. For the gross reaction of 2HMF + O → 2DFF + 2HO, there are three main reaction stages, , the oxidation of the first HMF to DFF with the reduction of [V(O)(DMA)] to [V(OH)(DMA)], the aerobic oxidation of [V(OH)(DMA)] to the peroxide [V(O)(DMA)], and the oxidation of the second HMF to DFF with the reduction of [V(O)(DMA)] to [V(O)(DMA)]. The rate-determining reaction step is associated with the C-H bond cleavage of -CH group of the first HMF molecule. The peroxide [V(O)(DMA)] species exhibits better oxidative activity than the initial [V(O)(DMA)] species, which originates from its narrower HOMO-LUMO gap. The counteranion Cl exerts promotive effect on the aerobic oxidation of HMF to DFF catalyzed by [V(O)(DMA)] species.