Improving the hydrogen storage capacity of metal organic framework by chemical functionalization

The hydrogen storage capacity of transition metal decorated terphenyl linkers was investigated using density functional theory based M05-2X, M06 and wB97XD methods. The –OH and –SH groups are used as anchors to bind various transition metals such as Sc, Ti, V, and Cr on terphenyl linker. It has been found that each transition metal can bind four hydrogen molecules through Kubas interaction. The correlation between electron density at the bond critical point corresponding to H–H bond and concomitant intermolecular distances between transition metal and hydrogen molecules has been used to illustrate the Kubas mechanism. Further, to estimate the bulk storage capacity, 42 hydrogen molecules are allowed to interact with the new metal organic framework fragment in all possible binding sites. The calculated interaction energy per hydrogen molecule is found to be −3.38 kcal/mol. Comparison of this value with previous reports shows that this energy is suitable for room temperature hydrogen storage applications.