Superbase/Acylamido-Based Deep Eutectic Solvents for Multiple-Site Efficient CO2 Absorption

Deep eutectic solvents (DESs) have been regarded as promising alternative absorbents for CO2 capture recently. In this work, a series of novel superbase/acylamido-based DESs with low viscosity were synthesized and used for CO2 capture. 1,5-Diazabicyclo[4.3.0]non-5-ene (DBN)/2-imidazolidone (EU) (2:1) exhibited fairly high absorption capacity up to 23.02 wt % (1.75 mol CO2 per mol DES) at 45 °C and 1 bar. Furthermore, the absorbent showed high desorption efficiency and excellent recycling performance during five absorption–desorption cycles. Fourier transform infrared, 1H NMR, and 13C NMR spectra analyses and quantum chemical calculations were used to investigate the interaction mechanism between the DES and CO2. The enhanced CO2 absorption capacity can be ascribed to the strong multiple-site interaction between the N atom of EU and CO2. This work supplies a new strategy to design and optimize high-efficiency superbase/acylamido-based DESs for CO2 capture.