Solvents with appropriate acidity are required to simultaneously realize efficient and reversible absorption of NH 3 . To achieve this goal, a series of 1-ethyl-3-methylimidazolium ([emim]Cl)-based DESs with different weak acids as the hydrogen-bond donors (HBDs) were prepared and characterized. The acidities of these weak acids cover a wide range, with the pK a values in DMSO ranging from 8.2 to 18.6. The NH 3 absorption and desorption performance of DESs were investigated systematically and correlated with the acidities of HBDs. The different behavior of NH 3 absorption was analyzed by spectroscopic characterizations and thermodynamic calculations. By manufacturing the acidities of HBDs in DESs, solvents having not only high capacities but also good reversibility for NH 3 absorption were identified. The optimal DESs were then selected as representatives to investigate the effects of HBA to HBD molar ratios and temperatures on NH 3 absorption, as well as the selective absorption of NH 3 from other gases.

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