CO₂ emission from flue gas is an important issue threatening human survival. Deep eutectic solvents (DESs), which have many unique properties, have been studied for CO₂ capture. However, water can be absorbed by DESs during the absorption of CO₂, which may increase the energy cost during the desorption of CO₂. In this work, a new kind of hydrophobic functional DES formed by polyamine hydrochloride and thymol was synthesized and used for CO₂ capture. It had been found that these DESs could efficiently capture CO₂ even at low partial pressures. The CO₂ capacity of [TEPA]Cl-thymol (n_[TEPA]Cl/n_thymol = 1:3) was high up to 1.355 mol CO₂/mol DES at 40 °C and 101.3 kPa. Interestingly, these DESs were still hydrophobic after saturated with CO₂. The CO₂ absorption capacity increased with a decrease of temperature and an increase of CO₂ partial pressure. Regeneration results showed that no obvious loss in the capacity could be found after five absorption/desorption cycles of these DESs. The Fourier transform infrared (FT-IR) spectra indicated that CO₂ could interact with amino in the DESs by the formation of carboxylate. Moreover, the equilibrium constant and Henry’s law constant in chemical absorption and physical absorption were studied.

This Special Issue, entitled “Advances in deep eutectic solvents: New green solvents”, was organized to collect original research articles on the latest developments in the new green solvents, deep eutectic solvents (DESs), and their applications