Adsorption of organic pollutants on B12N12 and Al12N12 nanocages

Abstract

The adsorption of twenty-four aromatic pollutants (1,3-dichlorobenzene, benzene, ethyl benzene, 1,4-dinitrobenzene, 4-fluorophenol, phenyl acetate, etc.) onto B₁₂N₁₂ and Al₁₂N₁₂ nanocages is studied using density functional theory. The pollutant molecules are typically bound to the B/Al atoms of the B₁₂N₁₂ and Al₁₂N₁₂ nanocages. Benzene and chlorine−/alkyl-substituted benzenes are observed to be weakly adsorbed on the B₁₂N₁₂ and Al₁₂N₁₂ nanocages. All other pollutant molecules are strongly adsorbed on the B₁₂N₁₂ and Al₁₂N₁₂ nanocages. Importantly, the adsorption energies are linearly proportional to the MESP minimum values of the pollutant molecules. A striking change in the reactivity parameter (e.g. global electrophilicity) of the B₁₂N₁₂ and Al₁₂N₁₂ nanocages is usually found for the adsorption of nitro-substituted aromatic compounds and carbonyl-containing compounds. The QTAIM analyses point to a noncovalent character for the interaction of benzene and chlorine−/alkyl-substituted benzenes with the B₁₂N₁₂ nanocage, and to a partial covalent character for the interaction of the other studied pollutant molecules with the B₁₂N₁₂ nanocage. However, an opposite trend is observed for the pollutant/Al₁₂N₁₂ system. Our results show a relatively high stability of the complexes of nitro-/OH−/carbonyl-containing compounds with B₁₂N₁₂ and Al₁₂N₁₂ in water.