N-substituted sumanene and cation-it interactions towards Li cations: A theoretical study

Understanding cation-'t interactions of different cations with'-bowl shaped carbon structures at atomic and molecular levels is decisive to design new materials. In the present work, adsorption of Li cations on the surfaces of sumanene and recently synthesized triazasumanene has been studied by using theoretical methods. Our computations have shown that Li+ can be adsorbed favorably on both sumanene and triazasumanene molecules. The obtained magnitudes of interaction energy (NO for sumanene in both concave (-40.48) and convex (-37.97 kcal/mol) positions are sufficiently larger than those for triazasumanene (-24.14, -22.15 kcal/mol, respectively). However, adsorption of Li+ on the N atom site of triazasumanene yields even larger E h , value (-46.97 kcal/mol) compared with sumanene. A detailed examination of the binding mechanism between Li + and sumanene (triazasumanene) has been carried out by symmetry-adapted perturbation theory. Thus, Li+ @sumanene attractive interactions are due to three energy constituents (electrostatic, inductive, and dispersive), whereas only inductive and dispersive energy terms contribute into attractive interactions of Li+@triazasumanene complexes. It has been established that Li+ at the sumanene surface is capable of uptaking four or five H-2 molecules per Li+. On the other hand, each Li+ at triazasumanene can attach up to five hydrogen molecules. Ab initio molecular dynamics simulations have approved stability of employed Li+@sumanene (triazasumanene) complexes, besides, they allow obtaining gravimetric densities (GDs, wt%) at various temperatures, and the maximal GDs have been calculated to be 6.1 wt% for Li+ -decorated sumanene and 9.5 wt% for Li+ decorated triazasumanene at liquid nitrogen temperature. In that regard, it is supposed that Li+ -decorated triazasumanene complex can be adopted as a promising hydrogen storage system.