Boosting the Activity of Catalytic Oxidation of 5-Hydroxymethylfurfural to 2,5-Diformylfuran Over Nitrogen-Doped Manganese Oxide Catalysts
Approaches for the catalytic oxidation of biomass-based 5-hydroxymethylfurfural (HMF) into valuable chemicals are in great demand but their development is still challenging. Here we present nitrogen-doped manganese oxide (N-MnO2) catalysts that possess extraordinary catalytic performance (>99.9% 2,5-diformylfuran selectivity, 100% HMF conversion, decent reusability) at room temperature without any additive. The structure changes after nitrogen doped into MnO2 reflected in two aspects: slightly elongation of the Mn-O bonds and reduction of the coordination number of Mn sites, as confirmed by characterization of extended X-ray absorption fine structure (EXAFs), H2-temperature programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). Mechanistic studies indicate that surface defect sites and coordinatively unsaturated Mn sites induced by nitrogen doping play a key role in promoting oxidative activity.