Properties and applications of choline-based deep eutectic solvents

Choline-based deep eutectic solvents (DESs) are considered as a new class of ionic liquids. Comparing to traditional ionic liquids, choline-based DESs are low-toxic, biodegradable, and the price is generally low, which make them more and more attractive in green chemistry and industrial chemistry. In the current work, the properties of choline-based DESs, such as freezing point, melting point, solubility, viscosity, surface tension and conductivity, were collected and summarized. The dependences of these properties with different factors, such as temperature, mole ratios and water content, and the models which can be used to predict the properties were studied and discussed. The applications of choline-based DESs in the area of lubrication, functional material preparation, electrochemistry, organic synthesis and catalytic conversion of biomass were introduced. Finally, the problems and difficulties in research and applications were illustrated and then prospective was provided.