The separation and purification of light hydrocarbons is challenging in the industry. Recently, a ZJNU-30 metal-organic framework (MOF) has been found to have the potential for adsorption-based separation of olefins and diolefins with four carbon atoms [H. M. Liu et al. Chem. - Eur. J. 2016, 22, 14988-14997]. Our study corroborates this finding but reveals Fe-MOF-74 as a more efficient candidate for the separation because of the open metal sites. We performed adsorption-based separation, transient breakthrough curves, and density functional theory calculations. This combination of techniques provides an extensive understanding of the studied system. Using this MOF, we propose a separation scheme to obtain a high-purity product.

An increase in demand for energy efficient processes for the separation of saturated and unsaturated light hydrocarbons mixtures drives the need of noncryogenic processes. The adsorptive separation using Metal-Organic Frameworks with coordinatively unsaturated metal sites may provide a cost-effective alternative due to the strong binding of the metal cation with the unsaturated hydrocarbons. Since experiments on adsorption equilibrium of gas mixtures are challenging, we propose classical force field based simulations to analyse the ability of MOF-74 with different metal substitutions for the separation of C2 and C3 olefin/paraffin binary mixtures. We parametrized the force field by fitting to available experimental single-component adsorption isotherms of ethane, ethene, propane, and propene in M–MOF-74 (M=Co, Fe, Mn, and Ni). The force field was validated for a variety of temperatures ranged from 273 K to 353 K. We then conducted Monte Carlo simulations in the Grand-Canonical ensemble to elucidate the adsorption mechanisms of the saturated/unsaturated hydrocarbon mixtures, at 318 K and 353 K. We computed the adsorption isotherms, and from these the adsorption selectivity, and addressed the variations of MOF properties with different metal cations. Fe-based MOF-74 appears the best option for both ethane/ethene and propane/propene separation applications. This finding partly agrees with previous work based on the Ideal Adsorbed Solution Theory.