Efficient strategy for fructose conversion to 2,5-furandicarboxylic acid, 2,5-dicarbonylfuran or 5-formyl-2-furancarboxylic acid over dual single-atomic Fe/Co catalyst

Abstract

5-Hydroxymethylfurfural (HMF), which is obtained from fructose dehydration, can be oxidized to valuable biomass-based platform chemicals, such as 2,5-furandicarboxylic acid (FDCA), 2,5-dicarbonylfuran (DFF) and 5-formyl-2-furancarboxylic acid (FFCA). However, the complex reactions of dehydration and oxidations make it is still challenging to obtain these chemicals from fructose. Herein, a dual single-atomic Fe/Co composed of isolated FeN6 and CoN5 sites supported on N-doped carbon (Fe/Co-NC) was constructed to efficient conversion of fructose to FDCA, DFF or FFCA through a two-step strategy. Owing to the Lewis acid sites in Fe/Co-NC, fructose can efficiently convert to HMF with an isolated yield of 91.70 % at 145 °C in dimethyl sulfoxide (DMSO). Furthermore, synergistic effect between Fe and Co atoms, which results in charge redistribution, can also promote the adsorption and activation of HMF and O2 for efficient oxidation. Attributing to the various ability of Fe/Co-NC to activate O2 in different solvents, superoxide radicals (·O2−) generated in MeCN result in 97.70 % yield of DFF, while peroxyl radicals (·OOH) generated in water lead to 97.29 % yield of FDCA. Adding DMSO in aqueous system seriously hinders the reaction rate (rate constant from 0.0022 to 0.0008 min−1) due to solvation of HMF by DMSO, resulting in high yield of FFCA (81.56 %) at 4 h. Therefore, controllable conversion of FDCA, DFF or FFCA from fructose is achieved over Fe/Co-NC, and the readily recovered method and good stability of the catalyst also indicate the prospect for continuous production of the above chemicals from fructose in the future.