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 adsorption enthalpy in the range -15 to -20 kJ/mol can be achieved, leading to a high storage capacity at room temp. and pressures of up to 100 bar. Such materials could similarly be of utility in boosting the methane storage capacity in the tanks of natural gas-powered cars operating at reduced pressures of up to 35 or 65 bar. Particular attention will be devoted to recent results involving efforts to achieve new materials in which multiple H2 or CH4 mols. can adsorb at a single metal site, and in which the thermal management requirements assocd. with gas adsorption/desorption can be reduced.