Hydrogen storage in metal-organic framewords

Materials exhibiting reversible hydrogen adsorption with high gravimetric and volumetric capacities are sought for use in on-board storage systems of hydrogen fuel cell-powered vehicles. Microporous metal-organic frameworks with high internal surface areas have been shown to display excellent storage properties, but only at cryogenic temperatures. Methods for synthesizing frameworks containing coordinatively-unsaturated metal centers are therefore being developed as a means of increasing the H₂ adsorption enthalpy. In particular, we seek to synthesize thermally-robust, high-surface area materials with a high concentration of open metal coordination sites. By adjusting the electronic structure of the metal ions, it is expected that an optimal H₂ binding enthalpy in the range 15-20 kJ/mol can be achieved, leading to a high H₂ storage capacity at room temperature and safe pressures of up to 100 bar. Our approaches involve the insertion and activation of metal carbonyl units on the aromatic components of existing frameworks, as well as the design of new frameworks using bridging ligands that facilitate the generation of open metal coordination sites.