Adsorption of alkali and alkaline earth ions on nanocages using density functional theory

Abstract

The adsorption of alkali and alkaline earth ions onto the exterior surface of inorganic nanocages X12Y12 (X = B, Al, Ga and Y = N, P, As) was investigated by using the density functional theory (DFT). All of the configurations, including the pristine ions or nanocages, as well as the ion adsorbed nanocage systems, were optimized using B3LYP-D3 functional and DEF2-TZVP basis sets. Comparative single point energy calculations were performed using different functionals viz. B3LYP-D3, M06-2X, ωB97XD and CAM-B3LYP, together with DEF2-TZVP and DEF2-QZVP basis sets. The results of natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM), and non-covalent interaction (NCI) analyses were compatible with the results of electronic properties. Total density of states (TDOSs), the natural charge, Wiberg bond index (WBI), natural electron configuration, donor–acceptor NBO interactions and second-order perturbation energies are obtained. Strong interaction between the ions and the nanocages is observed and the tendency of the ions to adsorb onto the surfaces of the mentioned X12Y12 nanocages is in the order Be++ > Mg++ > Ca++ > Li+ > Na+ > K+. These nanocages may be potential sensors for these alkali and alkaline earth ions.