[BMIM][PF₆] Incorporation Doubles CO₂ Selectivity of ZIF-8: Elucidation of Interactions and Their Consequences on...

Experiments were combined with atomically detailed simulations and density functional theory (DFT) calculations to understand the effect of incorporation of an ionic liquid (IL), 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]), into a metal organic framework (MOF with a zeolitic imidazolate framework), ZIF-8, on the CO₂ separation performance. The interactions between [BMIM][PF₆] and ZIF-8 were examined in deep detail, and their consequences on CO₂/CH₄, CO₂/N₂, and CH₄/N₂ separation have been elucidated by using experimental measurements complemented by DFT calculations and atomically detailed simulations. Results suggest that IL-MOF interactions strongly affect the gas affinity of materials at low pressure, whereas available pore volume plays a key role for gas adsorption at high pressures. Direct interactions between IL and MOF lead to at least a doubling of CO₂/CH₄ and CO₂/N₂ selectivities of ZIF-8. These results provide opportunities for rational design and development of IL-incorporated MOFs with exceptional selectivity for target gas separation applications.