First principle calculations on the adsorption of molecular H2 in the largest pore of Co[Fe(CN)5NO] and Ni[Fe(CN)5NO] metal nitroprussides. Effect of the charged cavities on the adsorption and H2-host interactions

Abstract The adsorption of H 2 inside the largest cavity of the anhydrous cubic phases Ni[Fe(CN) 5 NO] and Co[Fe(CN) 5 NO] has been analyzed using density functional theory. The H 2 -host interactions, geometries and electronic properties have been studied from first principle calculations. The effect of the charged cavities has also been analyzed with increasing numbers of H 2 molecules inside these materials. The largest adsorption energies were obtained for the charged cubic-Co cavity with six hydrogen molecules. The analysis of bands and projected density of states demonstrates the existence of the Kubas-type interaction in both charged Ni and Co cubic cavities. Atom in Molecules analysis shows important non-covalent interactions such as H…H, H…C and H…N while NBO helps to understand the experimental trends in ν C N stretching frequencies. Theoretical phonons analysis reveals the Kubas-type interaction and is in agreement with experimental IR-spectra of these solids.