Gas-Phase Interaction of CO, CO 2 , H 2 S, NH 3 , NO, NO 2 , and SO 2 with Zn 12 O 12 and Zn 24 Atomic Clusters.

Atmospheric pollutants pose a high risk to human health, and therefore it is necessary to capture and preferably remove them from ambient air. In this work, we investigate the intermolecular interaction between the pollutants such as CO, CO 2 , H 2 S, NH 3 , NO, NO 2 , and SO 2 gases with the Zn 24 and Zn 12 O 12 atomic clusters, using the density functional theory (DFT) at the meta-hybrid functional TPSSh and LANl2Dz basis set. The adsorption energy of these gas molecules on the outer surfaces of both types of clusters has been calculated and found to have a negative value, indicating a strong molecular-cluster interaction. The largest adsorption energy has been observed between SO 2 and the Zn 24 cluster. In general, the Zn 24 cluster appears to be more effective for adsorbing SO 2 , NO 2 , and NO than Zn 12 O 12 , whereas the latter is preferable for the adsorption of CO, CO 2 , H 2 S, and NH 3 . Frontier molecular orbital (FMO) analysis showed that Zn 24 exhibits higher stability upon adsorption of NH 3 , NO, NO 2 , and SO 2 , with the adsorption energy falling within the chemisorption range. The Zn 12 O 12 cluster shows a characteristic decrease in band gap upon adsorption of CO, H 2 S, NO, and NO 2 , suggesting an increase in electrical conductivity. Natural bond orbital (NBO) analysis also suggests the presence of strong intermolecular interactions between atomic clusters and the gases. This interaction was recognized to be strong and noncovalent, as determined by noncovalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analyses. Overall, our results suggest that both Zn 24 and Zn 12 O 12 clusters are good candidate species for promoting adsorption and, thus, can be employed in different materials and/or systems for enhancing interaction with CO, H 2 S, NO, or NO 2 .