Biochar catalysts for efficiently 5-Hydroxymethylfurfural (HMF) synthesis in aqueous natural deep eutectic solvent (A-NADES)

This study prepared a series of biochar-based catalysts using different parts of Larix principis-rupprechtii as feedstock, to promote the 5-Hydroxymethylfurfural (HMF) synthesis from glucose and fructose. Sulfonated biochar showed high converting efficiency of fructose in both dimethyl sulfoxide (DMSO) and aqueous-natural deep eutectic solvent (A-NADES) reaction systems, with HMF yield of 96.3% prepared from the pine needle-derived acidic catalyst under mild condition. Bifunctional acidic biochar catalysts containing both Lewis acid and Bronsted acid functional groups could effectively enhance the glucose conversion with 57.2% of the HMF yield obtained in A-NADES. After the detailed characterization of the biochar catalysts, the potential mechanism of the bifunctional catalyst for the synthesis of HMF by conversion of glucose and fructose was proposed. The possible promoting mechanism of carbohydrate conversion by A-NADES through intermolecular hydrogen bonding was also explored.