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 Ca 2+ -based metal–organic framework (MOF) [Ca(dtztp) 0.5 (DMA)]·2H 2 O ( 1 ) was constructed using the N, O -donor ligand 2,5-di(2 H -tetrazol-5-yl)terephthalic acid and the less-studied alkaline earth Ca 2+ 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 C 2 H 2 and selectivity for C 2 H 2 over CO 2, C 2 H 4, C 2 H 6, and CH 4 . Dynamic breakthrough experiments indicated the actual C 2 H 2 separation potential of the MOF from binary (C 2 H 2 –C 2 H 4 and C 2 H 2 –CO 2 ) and ternary (C 2 H 2 –C 2 H 4 –CO 2 and C 2 H 2 –C 2 H 4 –C 2 H 6 ) mixtures. Simulations revealed that the synergistic interactions between the OMSs and N atoms in MOF and C 2 H 2 molecules play an important role in the separation of C 2 H 2 .