Molecular engineering of a MOF with an ionic liquid sheath for direct air separation at ambient conditions

Combining ionic liquids (ILs) with metal–organic frameworks (MOFs) offers broad prospects for gas separation applications. However, identifying the best IL-MOF pair for a target gas separation solely based on experimental techniques is impractical. Herein, the promising IL and MOF combination was selected among 35,672 distinct ILs and 5,629 different MOFs by fusing computational methods at different molecular scales, density functional theory, conductor-like screening model for real solvents calculations, and grand canonical Monte Carlo simulations to engineer a MOF with an IL sheath (MOFILS) for direct air separation. The new MOFILS composed of [P6,6,6,14][DCA] and PCN-250(Fe) designed at the atomic level was then experimentally synthesized after fine-tuning the MOF to achieve high-performance air separation. An exceptionally high ideal O2/N2 selectivity of 26 was reached at 1 bar and 25 °C, boosting the benchmark value by four-times. The results of equilibrium and dynamic gas adsorption measurements further indicated a remarkably high selectivity of 382 for the separation of O2/N2:21/79 mixture, demonstrating the broad potential of the MOFILS designed in this work for direct air separation.