Efficient and reversible absorption of ammonia by cobalt ionic liquids through Lewis acid-base and cooperative hydrogen bond interactions

Ammonia (NH 3 ) emissions have caused a wide range of environmental problems and serious harm to human health. However, efficiently separating NH 3 and simultaneously recovering high purity NH 3 easily remains a great challenge. A new strategy to design transition metal ionic liquids (MILs) by combining specific metal centers and ligands with ILs was proposed for efficient and reversible absorption of NH 3 . Not only exceptional NH 3 absorption capacity and high NH 3 /CO 2 selectivity, but also excellent recyclability were achieved by cobalt ILs [C n mim] 2 [Co(NCS) 4 ]. The maximal capacity of NH 3 is up to 6.09 mol NH 3 mol IL −1 at 30 °C and 0.10 MPa, which is much higher than all reported ILs to date, and is over 30 times higher than the conventional ILs [C n mim][SCN]. The superior NH 3 capacity and desorption performance originate from the moderate Lewis acid-base and cooperative hydrogen bond interactions between the metal center-ligands and NH 3 . Cobalt ionic liquids with highly efficient and reversible absorption of NH 3 through Lewis acid-base and hydrogen bond interactions were designed.