LAUSR

Eight new members of two series of PEG-6000-bridged geminal dicationic ionic liquids based on diphenylammonium/imidazolium cation were synthesized by the change of four anions $$\hbox {CF}_{3}\hbox {COO}^{-}$$CF3COO-, $$\hbox {CCl}_{3}\hbox {COO}^{-}$$CCl3COO-, $$\hbox {AcO}^{-}$$AcO- and $$\hbox {HSO}_{4}^{-}$$HSO4-. They were investigated as reusable acidic catalysts for dehydration of fructose to 5-hydroxymethylfurfural in polar aprotic solvent. The characterizations of dicationic ionic liquids were done using $${}^{1}\hbox {H NMR}$$1H NMR, $${}^{13}\hbox {C NMR}$$13C NMR, IR and TGA analyses. Irrespective of Hammett acidity strength of the eight ILs, they displayed single peak selectivity for the 5-hydroxymethyl furfural intermediate in HPLC analysis.Graphical AbstractTwo series of N-sulfonic acid functionalized PEG-6000 bridged geminal dicationic diphenylammonium/imidazolium ionic liquids were developed in pair with $$\hbox {CF}_{3}\hbox {COO}^{-}$$CF3COO-, $$\hbox {CCl}_{3}\hbox {COO}^{-}$$CCl3COO-, $$\hbox {AcO}^{-}$$AcO- and $$\hbox {HSO}_{4}^{-}$$HSO4- anions. Single peak selectivity of 5-hydroxymethylfurfural in HPLCs was observed from dehydration of fructose in polar aprotic solvent using these acidic ionic liquid catalysts.