Adsorption of gases on B₁₂N₁₂ and Al₁₂N₁₂ nanocages

Density functional theory (DFT) was used to investigate the adsorption of twenty-four gases (SiH₄, H₂, Cl₂, F₂, CF₄, CH₄, CF₂Cl₂, N₂, CHF₃, OCS, N₂O, AsH₃, CH₃Cl, COCl₂, C₂H₂, C₂H₄, H₂Se, H₂S, PH₃, COF₂, CH₃F, HCHO, (CH₃)₂O, and CH₃NH₂) on B₁₂N₁₂ and Al₁₂N₁₂ nanocages. Most of the studied gases are weakly (strongly) adsorbed on the B₁₂N₁₂ (Al₁₂N₁₂) nanocage. However, AsH₃, H₂Se, H₂S, PH₃, CH₃F, HCHO, (CH₃)₂O, and CH₃NH₂ are strongly adsorbed on the B₁₂N₁₂ nanocage and H₂, F₂, CF₄, CH₄, and CF₂Cl₂ are weakly adsorbed on the Al₁₂N₁₂ nanocage. The most negative-valued molecular electrostatic potential (MESP) minimum (V_min) corresponds to the electron-rich region (e.g., lone pair and π-bond) in the molecule. An important observation is that the adsorption energies of the gases on the B₁₂N₁₂ and Al₁₂N₁₂ nanocages are well correlated with the MESP V_min values of the gases. Substantial changes are found in the DFT reactivity indices like chemical potential and hardness of the B₁₂N₁₂ and Al₁₂N₁₂ nanocages, mainly due to the strong gas adsorption. The quantum theory of atoms in molecules analysis suggests the covalent nature of interactions only in the AsH₃/B₁₂N₁₂, H₂Se/B₁₂N₁₂, H₂S/B₁₂N₁₂, and PH₃/B₁₂N₁₂ systems.