Mechanical Control of the Kinetic Propylene/Propane Separation by Zeolitic Imidazolate Framework-8

One intriguing feature of many porous MOFs is their stimulus-induced flexibility, which makes them unique compared to standard adsorbents. Here we propose an innovative concept to achieve an efficient kinetic separation of species with similar properties by the mechanical fine-tuning of the pore architecture of the flexible zeolitic imidazolate framework ZIF-8. This unprecedented approach was applied to one of the most challenging societally relevant separations: the separation of propylene and propane, which is of vital importance in the petrochemical industry. It was demonstrated that the application of an external pressure creates a gradual enhancement in the propylene/propane diffusion selectivity to more than one order of magnitude at 1 GPa pressure. A detailed analysis of the molecular simulations was further able to unravel the origin of this unusual behavior at the atomistic level.