An in silico study of the selective adsorption and separation of CO2 from a flue gas mixture (CH4, CO2, N2) by ZnLi5+ clusters.

Abstract

Due to the increasing concentration of CO2 in the atmosphere and its negative effect on the environment, selective adsorption of CO2 from flue gas has become significantly important. In this study, we have considered a Zn-doped lithium cluster, ZnLi5+ cluster, featuring a planar pentacoordinate Zn centre, as a potential candidate for selective CO2 capture and separation from a flue gas mixture (CH4, CO2, N2). The binding energy calculation and non-covalent interaction study showed that CO2 molecules bind relatively strongly as compared to N2 and CH4 molecules. The metal cluster can bind five CO2, five CH4, and four N2 molecules with average binding energies of -9.2, -4.4, and -6.1 kcal mol-1, respectively. Decomposition of the binding energy through symmetry-adapted perturbation theory analysis reveals that the electrostatic component plays a major role. The cationic cluster may be a promising candidate for selective CO2 capture and can be used as a pollution-controlling agent. The calculated adsorption energy of H2S is quite closer to that of CO2, suggesting competitive adsorption between CO2 and H2S. The adsorption energies of H2O and NH3 are higher compared to CO2, indicating that these gases may be a potential threat to CO2 capture.