Superior Selective and Fast NH3 Adsorption of Soft Porous MOF/Ionic Liquid Composites with Ordering Phase Transitions.

Efficient NH3 capture remains a significant and unresolved challenge, despite its critical importance for resource utilization and sustainable development. To achieve this goal, adsorbents simultaneously featuring high capacity, superior selectivity, and rapid adsorption kinetics are highly desired. In this work, we developed ionic liquid-loaded metal-organic framework (MOF/IL) composites by integrating highly NH3-affinitive functional IL with anthracene-based MOFs featuring diffusion-facilitated channels. Benefiting from the ordering phase transitions of space-confined IL-NH3, the composite presents a unique "S-shaped NH3 adsorption isotherm" and high volumetric NH3 uptake of 455.81 cm3/cm3 at 298 K and 1 bar. Moreover, the additionally created pathways decorated with a high density of ionic sites localized within the original MOF enable the specific recognition of NH3 molecules while facilitating NH3 transport throughout the composite matrix, thereby ensuring both high selectivity and fast adsorption kinetics. Overall, this work offers a new paradigm and an easy method for designing functional soft porous materials for efficient gas capture.