Hydrogen storage in metal-organic frameworks

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-org. frameworks with high internal surface areas have been shown to display excellent storage properties, but only at cryogenic temps. Methods for synthesizing frameworks contg. coordinatively-unsatd. 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 concn. 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 temp. and safe pressures of up to 100 bar. Our approaches involve the insertion and activation of metal carbonyl units on the arom. components of existing frameworks, as well as the design of new frameworks using bridging ligands that facilitate the generation of open metal coordination sites.