In this study, we developed a highly efficient catalytic system using dicationic ionic liquids. This system features dual Brønsted acid sites and four bromide ion sites, enabling the conversion of fructose to 2,5-diformylfuran (DFF) with a high yield in dimethyl sulfoxide at 140 °C for 4 h.

Abstract

2,5-Diformylfuran (DFF) is an essential building block in organic synthesis and a precursor for various chemical reactions. The one-pot, one-step synthesis of DFF from biomass-derived substrates has attracted significant interest due to its potential for cost-effective, scalable industrial applications. In this study, we developed a cost-effective method to synthesize a bifunctional catalyst, [(C₉H₁₆N₂)₂-(C₄H₈)₃-(SO₃H)₂][Br₄], through the combination of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,4-dibromobutane, 1,4-butanesultone, and hydrobromic acid. This catalyst was subsequently employed for the one-pot oxidation–dehydration of fructose to DFF. The structure of the ionic liquid catalyst was determined by methods such as NMR and FTIR, and the thermal stability of the catalyst was analyzed using the TGA method. The catalyst structure consisted of Brönsted and oxidative centers, which enhanced DFF yield by about 99% with an ionic liquid catalyst (10 mol%) in DMSO at 140 °C after 4 h. The manufacturing process of DFF from fructose via the two subsequent steps skips the stage of HMF isolation, saving effort and time. Furthermore, the reusability of the catalyst was researched, with the second recovery efficiency above 50% of DFF. This work provided a process to prepare DFF using ionic liquid as a catalyst, an environmentally friendly method with a good DFF yield.