Conversion of 5-Hydroxymethylfurfural and Carbohydrates to 2,5-Diformylfuran Over MoOx/Biochar Catalysts

Here, a series of nitrogen-doped carbon (NC) supported transition metal oxide catalysts were prepared by pyrolysis of chitosan-metal salt mixtures for the efficient synthesis 2,5-diformylfuran (DFF) from 5-hydroxymethylfurfural (HMF) and fructose. Among them, supported molybdenum-based species on nitrogen-doped carbon (Mo/NC) exhibited excellent activity and selectivity for selective oxidation of HMF to DFF. The presence of nitrogen species reduces the electron cloud density around the Mo species, thereby improving the catalytic activity. Moreover, the interaction between active MoO₂ species on the catalyst surface and NC ensured the stability of the catalyst, resulting in no significant loss of activity after four catalytic cycles. 99.5 % and 55.1 % yields of DFF with full conversion were obtained from HMF and fructose respectively over Mo/NC-chitosan-600 in DMSO under ambient air. In order to enhance DFF yield from fructose, sulfonate groups were introduced into Mo/NC-chitosan-600 catalyst, leading to the highest DFF yield of 70.2 %. In addition, this catalyst also allowed 10.0%, 22.9% and 33.3% DFF yields from glucose, sucrose and inulin, respectively.