Confining organic cations in metal organic framework allows molecular level regulation of CO₂ capture

High tunability of both ionic liquids (ILs) and metal organic frameworks (MOFs) enables great opportunity in the rational designation of IL/MOF composites for physical adsorption and separation. Traditionally, cations and anions of ILs as an entirety are combined with MOFs either inside or outside the microchannels. Herein, organic cations of ILs were confined into Cu-BTC and the champion adsorbent is obtained by using 1-propionic acid-3-vinylimidazole bromide as the precursor with a moderate loading amount, exhibiting higher CO₂ uptakes of 8/5 mmol g⁻¹ than Cu-BTC (6.0/3.5 mmol g⁻¹) at 273/298 K and 100 kPa, associating with significantly improved CO₂/N₂(CH₄) selectivities. The organic cations are interacted with two adjacent CuII₂(CRO₂)₂ paddle wheel units of Cu-BTC, expanding the Cu-O bond to strengthen the CO₂ affinity of open Cu sites and also serving as an additive CO₂ adsorptive site. The promotion of CO₂ capture ability is further reflected in the dynamic column breakthrough experiment.