Molecular simulation of propane/propylene separation on the metal–organic framework CuBTC

We present results of molecular simulation of pure propane and propylene, as well as their binary mixtures in the metal-organic framework CuBTC. By comparing simulated and experimental pure-component isotherms we are able to describe the adsorption mechanism of these two molecules. The main difference is the existence of strong specific interactions between the open metal sites of CuBTC, freed by framework dehydration during the activation process, and the pi orbitals of the propylene double bond. The net result is a moderate selectivity (up to 4) of the material for propylene adsorption. Given the current lack of experimental data for propane/propylene mixture adsorption in CuBTC, we have compared the molecular simulation results to predictions from Ideal Adsorbed Solution Theory using single-component experimental adsorption isotherms as input. Our comparison suggests that IAST is likely to adequately describe this system, and differences between the theory and simulation are probably due to shortcomings of the simplified potential model used to represent the pi-metal interactions.