Designing neoteric acidic deep eutectic solvents: an innovative, low-cost and environment-friendly strategy in the fast and facile production of 5-hydroxymethylfurfural

Abstract

5-Hydroxymethylfurfural (5-HMF), considered to be a versatile key precursor for the production of fine chemicals, is directly produced by the acid-catalyzed dehydration of fructose. The main drawback of 5-HMF is its instability. In fact, both its facile rehydration and the formation of insoluble humins are major concerns. Thus, simple, fast, and practical methods to prepare 5-HMF have attracted increasing attention. In this study, an unprecedented and neoteric type of natural deep eutectic solvents (NADES) composed of several carboxylic acids were synthesized and fully characterized to fast, one-pot, and facile production of 5-HMF. The effect of the acidity of NADESs on the 5-HMF yield was measured by Hammett acidity functions. The obtained acidic NADESs played a concomitant role of recyclable and sustainable solvent and catalyst for the dehydration of fructose under mild conditions, giving 5-hydroxymethylfurfural (5-HMF) in 90–97% within 1–2 min. This is the fastest process to be reported to date for 5-HMF production.