CO₂Adsorption On The B₁₂N₁₂ Nanocage Encapsulated With Alkali Metals:A Density Functional Study

The greenhouse effect caused by the emission of carbon dioxide（CO₂）has been a serious global problem due to the world economies relying on fossil fuels as energy source.Presently,utilizing non-metal materials for the adsorption of CO₂ as an alternative to precious metal catalyst is gaining interest,owing to their lower price as well as better durability.Density functional theory（DFT）calculations have been carried out to study the capacity of the B₁₂N₁₂2 nano-cage encapsulated with alkali metals（Li,Na,K）for the CO₂ adsorption and activation.It is found that after encapsulating alkali metals,the alkali metal atoms are closer to one side of clusters instead of exactly lying at the center,and a considerable charge transfers from the inner alkali metal atoms to the B₁₂N₁₂2 cage.Besides,the HOMO–LUMO gap（HLG）values of Li@B₁₂N₁₂,Na@B₁₂N₁₂2 and K@B₁₂N₁₂2 are decreased to about 6 eV,being much smaller than that of the pristine B₁₂N₁₂.Although the geometry structure parameters and the energy differences of M06-2X are slightly different from the ones ofωB97X-D,some identical results of two kinds of functional can be obtained.CO₂can be adsorbed chemically and physically on majority bonds of all the clusters,except for some bonds with large change in bond length and bond indices.The encapsulation of alkali-metal atoms may enhance the physical and chemical adsorption of CO₂ on the surface of the clusters,in which Na@B₁₂N₁₂2 and K@B₁₂N₁₂are the most powerful physical and chemical adsorbent for CO₂,respectively.