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

Ionic liquids (ILs) are considered as prospective absorbents for NH3 separation and purification owing to extremely low vapor pressure, great affinity and structural tunability. Up to date, versatile ILs for NH3 absorption have been developed, but NH3 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 NH3 mass capacity, selectivity and keep stable reversibility using IL absorbents is still a great challenge. In this work, the triazole cationfunctionalized ionic liquids (TCFILs) by introducing multiple protic H sites into N-heterocyclic cations were firstly designed and synthesized for enhancing NH3 absorption. These TCFILs showed superhigh NH3 mass capacity up to 0.365 g NH3/g IL at 30 degrees 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 NH3/CO2 up to 182 and recycling stability. Such great comprehensive performances of NH3 absorption and separation were proved to originate from multiple hydrogen bonding between NH3 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 NH3.