Ab initio investigation of hydrogenation of endohedral X@(BN)16 complexes (X = Li+, Na+, K+, Mg2+, Ne, O2−, S2−, F−, Cl−)

The hydrogenation of endohedral X@B16N16 (X = Li+, Na+, K+, Mg2+, Ne, O2−, S2−, F−, and Cl−) complexes has been studied at the B3LYP/6-31G* level of density functional theory. The structures and properties of the most stable X@B16N16 and X@B16N16H32 complexes along with the size and charge of the endohedral species are discussed comprehensively from the aspects of the average B-N bond lengths, average binding energy per H2 molecule and inclusion energy. On the basis of computational results, it is found that the small and highly charged guest species is favorable for endohedral, and the average binding energies of hydrogenated X@B16N16 complexes are larger than that of B16N16 cage on the whole. Especially, Mg2+ encapsulation is favorable thermodynamically and it could obviously reduce the hydrogen adsorption barriers by 12.05 kcal/mol. Also, the reaction of Mg2+@B16N16 + 16H2 → Mg2+@B16N16H32 will reverse at 260 K, which is higher than the reversing temperature 110 K for the reaction of B16N16 + 16H2 → B16N16H32.