Designing metal organic framework/ionic liquid composite materials to enhance CH₄/N₂ selectivity via computational and experimental approaches

Abstract

In this work, we propose a computational and experimental approach to systematically select pyridine-based ionic liquids (IL) and examine their impact on the pore structure of CH₄/N₂ adsorption materials. Our objective is to design novel MIL-53(Al)@IL composites, with MIL-53(Al) as the parent metal organic framework (MOF), for efficient CH₄/N₂ separation. The optimal addition of pyridine-based ionic liquids resulted in the MIL-53(Al)@BH-3 (N-butylpyridinium hydrogen sulfate abbreviated as BH-3) composite, which features an ultramicropore structure and a large specific surface area of 1204 cm² g⁻¹. The MIL-53(Al)@BH-3 composite achieved a high CH₄ capacity of 28.21 cm³(STP) g⁻¹ and a selectivity of 7.7 at 298K and 1 bar in pure-component equilibrium adsorption. In breakthrough experiments, CH₄ breakthrough occurred significantly later than N₂ (approximately 2 min). Therefore, the strategy of manufacturing porous MIL-53(Al)@BH-3 composites effectively enhances the overall adsorption performance for CH₄/N₂ separation.