Porous multi-site ionic liquid composites for superior selective and reversible adsorption of ammonia

Ionic liquids (ILs) with low vapor pressure, tunable structures and good NH 3 affinity provide an inspiring way to efficiently capture NH 3 . However, the high viscosity of most ILs limited mass transfer, which incumbers their industrial applications. Besides, how to simultaneously achieve high selectivity, capacity and reversibility of NH 3 still face great challenge. Herein, four novel hydroxyl ammonium protic ILs (HAPILs), including methyldiethanolammonium trifluoromethanesulfonate ([MDEAH][CF 3 SO 3 ]), triethanolammonium trifluoromethanesulfonate ([TEAH][CF 3 SO 3 ]), dimethylethanolammonium trifluoromethanesulfonate ([DMEAH][CF 3 SO 3 ]) and diethylethanolammonium trifluoromethanesulfonate ([DEEAH][CF 3 SO 3 ]), with multiple hydrogen bonding donors that can interact with more over two NH 3 molecules were designed and synthesized, and were further supported onto porous molecular sieves to overcome the above problem. Among the prepared porous HAPIL composites, 50 wt% [TEAH][CF 3 SO 3 ]@MCM-41 showed the highest NH 3 /CO 2 selectivity of 62 under 313 K and 0.1 MPa compared with the state-of-the-art values, along with high capacity of 114.3 mgNH 3 /g-adsorbent. The excellent NH 3 adsorption performance was attributed to the synergistic interaction of mesoporous effect and multiple hydrogen bonding between NH 3 and HAPILs. Furthermore, the porous HAPIL composites exhibited great recyclability after six cycles, revealing great potentials in industrial application of efficient and reversible NH 3 separation.