In silico-directed design and experimental validation of an IL/UiO-66 nanocomposite with exceptional CO₂ selectivity across a wide pressure range

Abstract

Ionic liquid (IL)/metal-organic framework (MOF) (IL/MOF) nanocomposites have been shown to offer a broad potential in adsorption-based CO2 separation, especially at very low pressures. Selection of the most suitable ILs is crucial for synthesizing IL/MOF nanocomposites capable of achieving exceptionally high CO2 selectivities under more applicable conditions, such as at atmospheric pressure. However, the existence of a very wide range of IL-MOF pairs makes the design of such materials time-consuming when relying solely on experimental approaches. In this work, we employed a multitiered computational approach involving conductor-like screening model for realistic solvents, grand canonical Monte Carlo simulations, and density functional theory calculations. The goal was to screen 35,476 diverse ILs from various families to identify the IL that could boost the CO2 selectivity. Results of the computational screening highlighted 1-n-butyl-3-methylimidazolium tricyanomethanide ([BMIM][C(CN)3]) as the promising IL candidate offering significant potential for separation of CO2 from N-2 and CH4. We then experimentally incorporated this IL into a robust MOF, UiO-66, and characterized the resulting structure in deep detail. Testing of [BMIM][C(CN)(3)]/UiO-66 for adsorption of CO2, N-2, and CH4 demonstrated that the nanocomposite provides exceptional CO2 separation performance, offering an appreciable amount of CO2 uptake, while almost completely rejecting N(2 )and CH4 up to 1 and 0.3 bar, respectively, at 25 degrees C. Our results illustrated the importance of accurate selection of the IL for the design of IL/MOF nanocomposites with high performance for target gas separations.