Enabling high C2H2 storage and efficient C2H2/CO2 separation in a cage-like MOF with multiple supramolecular binding sites†

Separating acetylene (C₂H₂) from carbon dioxide (CO₂) is of great industrial importance for achieving high-purity C₂H₂ (>99%). However, overcoming the trade-off effect between adsorption capacity and selectivity remains a daunting challenge owing to their similar physicochemical properties. Herein, we present a novel cage-like metal–organic framework termed Cu-TPHC for efficiently purifying C₂H₂ from C₂H₂/CO₂ mixtures. Cu-TPHC exhibits a high C₂H₂ uptake (157.5 cm³ g⁻¹), C₂H₂/CO₂ selectivity (4.9), and a relatively low C₂H₂ adsorption enthalpy (29.6 kJ mol⁻¹) at 298 K. The excellent separation potential was demonstrated by breakthrough experiments for an equimolar C₂H₂/CO₂ mixture under various conditions, with good recyclability and a 99.4% purity of the recovered C₂H₂. Grand canonical Monte Carlo simulations reveal that the uncoordinated carboxylate oxygen atoms, coordinated water molecules and free OH⁻ anions provide multiple supramolecular binding sites that preferentially interact with C₂H₂ over CO₂.