Efficient and reversible absorption of CO2 was investigated by weak basic ionic liquid of butyltriethylammonium acetylacetonate ([N-2224][acac]) and polyethylene glycol 200 (PEG-200) mixtures with different mass ratios. The results showed that [N-2224][acac]/PEG-200 mixtures possessed a maximum absorption capacity of 0.9 mol CO2 per mole [N-2224][acac] at T = 298.15 K under ambient pressure. The mixtures used could be easily regenerated by bubbling N-2 through the solutions without obvious loss of absorption performance. Furthermore, the solubility data of CO2 in the mixtures at T = (303.15, 318.15, and 333.15) K under different pressures were measured. The thermodynamic parameters of absorption enthalpy and absorption entropy were calculated with resulting negative values at each condition. The mixtures showed low absorption enthalpy for CO2 capture. The addition of PEG-200 can accelerate absorption process. The CO2 capture process described using [N-2224][acac]/PEG-200 mixtures is a promising method for CO2 absorption with both good reversibility and high absorption capacity. (C) 2014 Elsevier Ltd. All rights reserved.