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

• Published in: Green chemistry : an international journal and green chemistry resource : GC Vol. 20; no. 9; pp. 2075 - 2083
• Main Authors: Zeng, Shaojuan, Liu, Lei, Shang, Dawei, Feng, Jianpeng, Dong, Haifeng, Xu, Qiuxia, Zhang, Xiangping, Zhang, Suojiang
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 2018
• Subjects: Absorption; Ammonia; Carbon dioxide; Cobalt; Design for recycling; Green chemistry; Hydrogen bonds; Ionic liquids; Ions; Lewis acid; Ligands; Metals; Recyclability
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/C8GC00215K

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 .