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.