CO2 capture is essential for both mitigating CO2 emissions and purifying/conditioning gases for fuel and chemical production. To further improve the process performance with low environmental impacts, different strategies have been proposed, where developing liquid green absorbent for capturing CO2 is one of the effective options. Ionic liquids (IL)/deep eutectic solvents (DES) have recently emerged as green absorbents with unique properties, especially DESs also benefit from facile synthesis, low toxicity, and high biodegradability. To promote their development, this work summarized the recent research progress on ILs/DESs developed for CO2 capture from the aspects of those physical- and chemical-based, and COSMO-RS was combined to predict the properties that are unavailable from published articles in order to evaluate their performance based on the key properties for different IL/DES-based technologies. Finally, top 10 ILs/DESs were listed based on the corresponding criteria. The shared information will provide insight into screening and further developing IL/DES-based technologies for CO2 capture.

The urgency of mitigating CO2 emissions has become increasingly critical due to their detrimental effects on environmental sustainability and human health. Among emerging solutions, deep eutectic solvents (DESs) have garnered attention for their high CO2 capture capacities. However, widespread application of DESs has been constrained by their inherent high viscosity and cost. To overcome these limitations, this study further explores the novel strategy, where cosolvent addition and immobilization are combined to develop a non-aqueous slurry for CO2 capture with high efficiency. Here, [MEACl][EDA] with (1:5) molar ratio is mixed with ethylene glycol (EG) to form a non-aqueous DES solution, and the DES is further immobilized into the mesoporous silica to form a composite and then mixed with the DES-EG solution to make a slurry. The CO2 capture tests demonstrated 15 wt.% capture capacity at 22 °C and 1 bar, and efficient sorption and desorption rates (0.34 and 0.38 mol CO2/(kg sorbent·min) within the initial 2 min). The slurry also exhibited promising cyclic performance with 96.4 % recovery together with minimal solvent loss of 0.97 % and almost intact structure after 120 hr of heating at 110 °C. The improved capture capacity and kinetics, especially for desorption, as well as enhanced thermal stability of the non-aqueous system highlight its potential for industrial applications.

Deep eutectic solvents (DES) emerge as a compelling class of ionic liquids, with distinct advantages over traditional solvents, particularly in the realm of CO2 capture. In the present study, [MEACl][EDA] is synthesized across various molar ratios (1:3 to 1:10) and combined with the results of Differential Scanning Calorimetry (DSC) to identify DESs. The DESs are further characterized using Fourier Transform Infrared Spectroscopy (FTIR), and the properties and performance of the DESs with diverse water contents (30–60 wt%) are systematically studied for CO2 capture. The optimal aqueous solution is identified based on the CO2 uptake and viscosity, followed by the evaluation of the cyclic absorption experiments. Results demonstrate that 40 wt% of [MEACl][EDA] DES with (1:5) molar ratio exhibits higher CO2 uptake (22.09 wt%) and comparable viscosity (4.401 mPa·s before and 13.330 mPa·s after CO2 capture at 25 °C) compared to aqueous 40 wt% MEA (15.74 wt% CO2 capture capacity, viscosity of 3.318 mPa·s before and 8.413 mPa·s after CO2 capture), and its absorption rate is also more favorable than the aqueous MEA. Furthermore, recycling studies reveal ∼ 88 % regeneration of the aqueous DES solution at 100 °C.

The urgent need to mitigate climate change and reduce greenhouse gas emissions has underscored the importance of developing effective CO2 capture technologies. In this study, a novel strategy was proposed and developed, where adding cosolvent and immobilizing deep eutectic solvent (DES) were combined to enhance the performance from capacity to rate. To this end, [MEACl][EDA] (1:5) was chosen as the DES, H2O was used as the cosolvent, and silica was selected as the substrate to immobilize the DES; the effects of the DES immobilization amount and the concentration of the immobilized DES particles in the aqueous system as well as temperature on the viscosity and CO2 capture performance were investigated systematically. Compared to the aqueous DES, the slurry exhibited higher CO2 uptake and improved kinetics, comparable viscosity before CO2 capture, and slightly high viscosity after CO2 capture, where the best sample (3 wt% of (5 wt% DES@silica) in 40 wt% aqueous DES) showed a capacity of 24.93 wt% at the room temperature (22 ℃) and viscosities of 7.32 and 21.82 mPa·s before and after CO2 capture. Also, the CO2 capture rate of the slurry reached 1.4 mol CO2/(kg sorbent·min) after 2 min at 22 ℃, which was higher than the aqueous DES without immobilized DES (1.24 mol CO2/(kg sorbent·min) under the same condition). The prepared slurries showed high stability (over one month) and high regeneration (∼91 % CO2 capture recovery after 5 cycles).