Effects of incorporated oxygen and sulfur heteroatoms into ligands for CO2/N2 and CO2/CH4 separation in metal-organic frameworks: A molecular simulation study

CO2 separations from flue gas and natural gas are important industrial issues. As energy-efficient alternative of traditional cryogenic method, equilibrium based CO2 separation by solid porous materials, i.e. metal organic frameworks (MOFs), has shown great potentials for CO2 separation. In this work, CO2/N2 and CO2/CH4 separation performance in three MOFs (UiO-67, Zr-BTDC, Zr-BFDC) with various heterocyclic ligands were investigated by grand canonical Monte Carlo (GCMC) simulations using first principle derived force field parameters. CO2/N2 and CO2/CH4 mixed gas separation results show that MOFs comprising oxygen heteroatoms on ligands (Zr-BFDC) is a promising material for CO2 separation from CO2/N2 and CO2/CH4 gas mixtures. Specifically, among the MOFs investigated, Zr-BFDC shows the highest uptake amounts of CO2 at low pressure range owing to high CO2 interaction affinity, while Zr-BTDC exhibits highest CO2 uptake amounts at high pressure range due to high accessible surface area. Moreover, Zr-BTDC and Zr-BFDC also show significantly enhanced CO2 selectivity over N2 and CH4 than their parent MOF, UiO-67, indicating their potential for practical CO2 separations.