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.