Adsorption of Gases on Fullerene-like X₁₂Y₁₂ (X = Be, Mg, Ca, B, Al, Ga, C; Y = C, Si, N, P, O) Nanocages

Density functional theory calculations are carried out to investigate the adsorption behaviors of CO₂, NO, CO, and NH₃ on 12 fullerene-like X₁₂Y₁₂ (B₁₂N₁₂, Al₁₂N₁₂, Ga₁₂N₁₂, B₁₂P₁₂, Al₁₂P₁₂, Ga₁₂P₁₂, Be₁₂O₁₂, Mg₁₂O₁₂, Ca₁₂O₁₂, C₁₂Si₁₂, C₁₂N₁₂, and C₂₄) nanocages. The molecular electrostatic potential (MESP) analysis suggests that, for example, for the B₁₂N₁₂, Al₁₂N₁₂, and Ga₁₂N₁₂ nanocages, the electron-rich regions are centered on the N atoms. The deepest MESP minimum (V_min) values suggest that replacement of C atoms in C₂₄ by XY units increases the electron-rich nature of the nanocage. Generally, CO₂ is found to be physisorbed, while NH₃ is chemisorbed on the X₁₂Y₁₂ nanocages. NO is found to be strongly adsorbed on the B₁₂P₁₂, Be₁₂O₁₂, Ca₁₂O₁₂, and C₂₄ nanocages, and CO is strongly adsorbed on the B₁₂N₁₂, B₁₂P₁₂, Be₁₂O₁₂, and C₂₄ nanocages. An important result is that the V_min values of the X₁₂Y₁₂ nanocages are linearly proportional to their CO₂ or NO adsorption energies. The quantum theory of atoms in molecules analysis suggests strong covalent interactions in the CO₂/Ca₁₂O₁₂, NO/Ca₁₂O₁₂, NO/C₂₄, CO/C₂₄, and NH₃/C₂₄ systems.