Amine-based deep eutectic solvents for CO2 capture: Experiments and molecular thermodynamics

Deep eutectic solvents (DESs) have shown great potential in capturing carbon dioxide (CO₂) and are expected to help alleviate the pressing issue of global warming. This study utilizes experimental approaches and molecular dynamics(MD) simulation to research the process of CO₂ capture with amine-based DESs. The DESs, composed of methyltriphenylphosphonium bromide (MTPPB) and methyldiethanolamine (MDEA) as the hydrogen bond acceptor (HBA) and donor (HBD), respectively, were evaluated for their physical properties and CO₂ absorption capacity. Additionally, the impact of different water contents and temperatures on CO₂ absorption was investigated. Results demonstrated that HBD quantity negatively correlates with viscosity while positively correlating with CO₂ solubility. The water content of the DESs ranged from 10 wt% to 50 wt%, leading to a progressive reduction in viscosity, while the CO₂ absorption capacity initially decreased and then increased. The DES with a molar ratio of 1:16 had the lowest viscosity of 10.5 mPa.s and the greatest CO₂ absorption of 0.1004 g CO₂/g DES at 50 wt% water content and 303.15 K, causing significant savings in solvent costs. MD simulations were utilized to explore the microscopic interactions among HBA, HBD, CO₂, and water, revealing that the addition of 50 wt% water does not affect the structure of the DES. The experimental and computational studies presented in this study illustrate that the introduction of a specific quantity of water to DESs and selecting suitable temperatures can enhance CO₂ capture efficiency, providing theoretical support for industrial application of CO₂ capture.