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Carbon capture and storage (CCS) technology is considered as one of the most effective short-term solutions in reducing atmospheric CO₂ concentrations. A key of CCS technology is to seek the absorbent with low cost, fast absorption rate, and high stability. In this study, we show that 2-ethyl-4-methylimidazole is particularly suitable for efficient CO₂ capture. The aqueous solution of 2-ethyl-4-methylimidazole displays a maximum CO₂ molar absorption capacity of 1.0 mol∙mol⁻¹ and the absorbed CO₂ can be completely released through heating the solution at a relatively low temperature (<100 °C). Stability tests show that the aqueous system is quite stable, with less than 10% loss of the molar absorption capacity after eight absorption–desorption cycles. Time-related <i>in-situ</i> attenuated total reflection infrared absorption spectroscopy and ¹³C nuclear magnetic resonance spectroscopy studies reveal that the intermediates are HCO₃⁻ and H₂CO₃ in the process of CO₂ absorption–desorption. These intermediates are easily decomposed, which are responsible for the low CO₂ desorption temperature and high desorption efficiency of the system. Moreover, the aqueous solution of 2-ethyl-4-methylimidazole is able to separate and purify CO₂ from flue gas and even ambient air. Consequently, 2-ethyl-4-methylimidazole is a promising low-cost CO₂ absorbent for industrial implementation.