Enhanced hydrogen uptake and the electronic structure of lithium-doped metal-organic frameworks

Metal-organic framework (MOF) materials show potential for gas separation and storage, and as hosts for highly selective catalyst molecules. Density functional theory (DFT) is applied to periodic band structures and to selected clusters representative of the cornerpost and strut environments of two MOFs to characterize the electronic environment. Binding sites and the binding energies of H₂ are calculated with and without the presence of a Li dopant. It is found that Li enhances the H₂ binding energies, both on the linking strut ring structures and for sites near cornerpost oxygen. MP2 correlation studies of the basic H₂-Li-bipyridine interaction are carried out to explore effects of correlation beyond DFT. Contrary to previous model assumptions, we find that Li associates strongly with the cornerposts and less so with aromatic rings.