Computational screening of hydrophobic metal–organic frameworks for the separation of H2S and CO2 from natural gas†
Natural gas is an environmentally friendly energy resource and it is of central importance to remove acid gases (e.g. H2S and CO2) from natural gas. In this study, we computationally screen 6013 metal–organic frameworks (MOFs) for the simultaneous separation of H2S and CO2 from natural gas under humid conditions (represented by a six-component CH4/C2H6/C3H8/H2S/CO2/H2O gas mixture). To minimize the competitive adsorption of H2O, 606 hydrophobic MOFs are first selected on the basis of the Henry constants of H2O and subsequently assessed for the adsorption capacity of H2S + CO2 (NH2S+CO2) and the selectivity of H2S + CO2 over C1–C3 (SH2S+CO2/C1–C3). Structure–performance relationships are established between MOF descriptors (the largest cavity diameter, surface area, void fraction and isosteric heat) and performance metrics (NH2S+CO2 and SH2S+CO2/C1–C3). Moreover, a new performance metric (TSN, the trade-off between NH2S+CO2 and SH2S+CO2/C1–C3) is proposed. From the Pearson correlation technique, it is revealed that the TSN has strong correlations with the MOF descriptors. Finally, the best MOFs are identified. Interestingly, most of the best MOFs contain N-rich organic linkers (e.g. pyridine and azoles), which are recommended for the design of functional MOFs for H2S and CO2 separation. The microscopic insights and guidelines provided by this computational study are useful toward the development of new MOFs for the efficient upgrading of natural gas.