Effects of anionic structure on the dissolution of cellulose in ionic liquids revealed by molecular simulation

Although ionic liquids (ILs) have shown promise in the pretreatment of cellulose and lignocellulosic biomass, there is no established rule to guide the rational design of such ILs up to date. In this work, the mixtures of cellulose with a series of ILs having the same cation [C2mim]+ but different anions have been simulated to study the effect of anionic nature on the dissolution of cellulose. It was shown that hydrogen bonds (HBs) were formed between anions of the ILs and hydroxyl protons of cellulose. Cl− anion and O atom of [CH3COO]− and [(CH3O)2PO2]− are better HB acceptors. Furthermore, the effects of electronegativity of HB acceptor atoms, steric effect of alkyl chain length and electron-withdrawing group of the anions on their HB acceptor ability have been investigated. The obtained results are expected to be important for the rational design of novel ILs for efficient dissolution of cellulose.