Enabling High C2H2 Storage and Efficient C2H2/CO2 Separation in a Cage-like MOF with Multiple Supramolecular Binding Sites

Abstract

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.