Acetylene Separation by a Ca-MOF Containing Accessible Sites of Open Metal Centers and Organic Groups

Efficient separation of acetylene from a ternary acetylene-containing mixture is an important and vital task in petrochemical industry, which is difficult to achieve using a single material. Herein, a new Ca2+-based metal-organic framework (MOF) [Ca(dtztp)0.5(DMA)]·2H2O (1) was constructed using the N,O-donor ligand 2,5-di(2H-tetrazol-5-yl)terephthalic acid and the less-studied alkaline earth Ca2+ ions. The MOF shows a 3D honeycomb framework based on unique metal-carboxylate-azolate rod secondary building units. Owing to the presence of high-density organic hydrogen-bonding acceptors and open metal sites (OMSs), the activated MOF shows high adsorption capacity for C2H2 and selectivity for C2H2 over CO2, C2H4, C2H6, and CH4. Dynamic breakthrough experiments indicated the actual C2H2 separation potential of the MOF from binary (C2H2-C2H4 and C2H2-CO2) and ternary (C2H2-C2H4-CO2 and C2H2-C2H4-C2H6) mixtures. Simulations revealed that the synergistic interactions between the OMSs and N atoms in MOF and C2H2 molecules play an important role in the separation of C2H2.