Propane/propylene separation in ion-exchanged zeolite-like metal organic frameworks

Propane/propylene separation performances of zeolite-like metal organic frameworks with rhombic and sodalite topologies (rho- and sod-ZMOFs) were estimated via Monte Carlo simulations over a wide range of pressure in order to evaluate their potential use in pressure swing adsorption applications. Extra-framework cation locations of the “as-synthesized” ZMOFs were identified based on the available experimental data. Selectivities and working capacities before and after the ion exchange of ZMOFs with Li+, Na+, and K+ ions were compared, by considering partially and completely ion-exchanged structures. Results showed that the difference in the dipole moments of propane and propylene is the dominant factor in separation and ion-exchanging enhances the propylene selectivity of ZMOFs. The enhancement is especially significant in sod-ZMOF structures for which a ten-fold increase in the selectivities was obtained, although their working capacities remained lower than those of rho-ZMOF structures.