New halloysite-supported bio-based acidic ionic liquid as an efficient catalyst for conversion of fructose to 5-hydroxymethylfurfural: A combined experimental and computational studies

In an effort to design a bio-based catalyst with enough acidic strength to promote the conversion of fructose to 5hydroxymethylfurfural, a series of halloysite clay-supported acidic ionic liquids were considered as potential candidates. The catalysts could be synthesized from reaction of Cl-functionalized halloysite with histidine, histamine, adenine and tryptophan, followed by treatment with chlorosulfuric acid. Predictive computational studies were performed and approved the superior activity of the histidine-based catalyst. In addition, the computational studies aimed to identify the optimal catalyst using Density Functional Theory (DFT) calculations and other characterization techniques, particularly non covalent interactions plots. Aknowledged by computational results, histidine based catalyst was prepared, characterized and its catalytic activity and recyclability were appraised for the synthesis of 5-hydroxymethylfurfural from fructose as a bio-based starting material. The reaction conditions were optimized and it was revealed that using 30 wt% catalyst, the desired product could be achieved at 100 degrees C within 1 h. Notably, the catalyst exhibited high recyclability and efficiently promoted the reaction of other mono-saccharides as well.