Core–Shell Type Ionic Liquid/Metal Organic Framework Composite: An Exceptionally High CO₂/CH₄ Selectivity

Here, we present a new concept of a core–shell type ionic liquid/metal organic framework (IL/MOF) composite. A hydrophilic IL, 1-(2-hydroxyethyl)-3-methylimidazolium dicyanamide, [HEMIM]­[DCA], was deposited on a hydrophobic zeolitic imidazolate framework, ZIF-8. The composite exhibited approximately 5.7 times higher CO₂ uptake and 45 times higher CO₂/CH₄ selectivity at 1 mbar and 25 °C compared to the parent MOF. Characterization showed that IL molecules deposited on the external surface of the MOF, forming a core (MOF)–shell (IL) type material, in which IL acts as a smart gate for the guest molecules.