Ultra-high NH3 absorption by triazole cation-functionalized ionic liquids through multiple hydrogen bonding

Ionic liquids (ILs) are considered as prospective absorbents for NH 3 separation and purification owing to extremely low vapor pressure, great affinity and structural tunability. Up to date, versatile ILs for NH 3 absorption have been developed, but NH 3 mass capacity of all the reported ILs or IL-based absorbents are still not comparable to that of traditional water absorbent. How to simultaneously improve NH 3 mass capacity, selectivity and keep stable reversibility using IL absorbents is still a great challenge. In this work, the triazole cation-functionalized ionic liquids (TCFILs) by introducing multiple protic H sites into N -heterocyclic cations were firstly designed and synthesized for enhancing NH 3 absorption. These TCFILs showed superhigh NH 3 mass capacity up to 0.365 g NH 3 /g IL at 30 °C and 1 bar, which is the maximum among the reported absorbents, and is even comparable to that of traditional water absorbent used in industrial. Moreover, the TCFILs also exhibited excellent selectivity of NH 3 /CO 2 up to 182 and recycling stability. Such great comprehensive performances of NH 3 absorption and separation were proved to originate from multiple hydrogen bonding between NH 3 and protic hydrogens of the TCFIL cations. Therefore, this work will provide useful guidance to design competitive functionalized ILs for efficient and reversible absorption of NH 3 .