Role of Ionic Liquid [EMIM]⁺[SCN]⁻ in the Adsorption and Diffusion of Gases in Metal–Organic Frameworks

We study the adsorption performance of metal–organic frameworks (MOFs) impregnated of ionic liquids (ILs). To this aim we calculated adsorption and diffusion of light gases (CO2, CH4, N2) and their mixtures in hybrid composites using molecular simulations. The hybrid composites consist of 1-ethyl-3-methylimidazolium thiocyanate impregnated in IRMOF-1, HMOF-1, MIL-47, and MOF-1. We found that the increase of the amount of IL enhances the adsorption selectivity in favor of carbon dioxide for the mixtures CO2/CH4 and CO2/N2 and in favor of methane in the mixture CH4/N2. We also provide detailed analysis of the microscopic organization of ILs and adsorbates via radial distribution functions and average occupation profiles and study the impact of the ILs in the diffusion of the adsorbates inside the pores of the MOFs. Based on our findings, we discuss the advantages of using IL/MOF composites for gas adsorption to increase the adsorption of gases and to control the pore sizes of the structures to foster selective adsorption.