Superbase Ionic Liquid-Based Deep Eutectic Solvents for Improving CO2 Absorption

Carbon dioxide (CO2) is a detrimental greenhouse gas to the environment as the main contributor to global warming. However, the development of efficient methods for CO2 absorption and separation is still a great challenge. Ionic liquids (ILs) have emerged as promising solvents for CO2 separation due to negligible vapor pressure and adjustable structures. In this work, a new strategy that three superbase ILs are designed as hydrogen bond acceptor (HBA) and further combined with ethylene glycol (EG) as hydrogen bond donor (HBD) to form novel IL-based deep eutectic solvents (DESs) was proposed for efficient and reversible absorption of CO2. The results indicated that both excellent recyclability and high CO2 mass capacity up to 0.141 g CO2/g DES under 40 degrees C and 100 kPa are achieved by [HDBU][Im]/EG with the mass ratio of 7:3, and the value is much higher than those of most of the reported IL-based DESs. The superior CO2 absorption and desorption performances were attributed to the synergistic interaction between both IL and EG with CO2 to form carbamate and carbonate, respectively. This work provides a feasible method for designing IL-based solvents in CO2 separation applications.