Aqueous-Natural Deep Eutectic Solvent-Enhanced 5-Hydroxymethylfurfural Production from Glucose, Starch, and Food Wastes.

5-Hydroxymethylfurfural (HMF) has been regarded as an essential building block for synthesizing chemicals and biofuels, but the direct conversion of biomass to HMF is still a critical challenge. In this study, a cheap and green aqueous-natural deep eutectic solvent (A-NADES) was used to efficiently produce HMF from various carbohydrates, with a low amount of SnCl as the catalyst. High HMF yields of 64.3, 64.0, 61.3, and 54.5 % were obtained from glucose, starch, rice waste, and bread waste at 130 °C in the A-NADES/MIBK (methyl isobutyl ketone) biphasic system, respectively. Mechanistic study results revealed that the water in A-NADES was the key factor in facilitating the conversion of Sn atom existent forms and promoted the HMF production. The choline chloride in NADES stabilized the HMF product with the cooperation of extraction solvent MIBK and inhibited the side reactions of HMF. This study investigated the multiple interaction functions of A-NADES to feedstocks and proposed a practical application of novel solvents to facilitate biomass and food waste conversion with a green method.