Strategies for increasing hydrogen storage capacity and adsorption energy in MOFs

Storage of hydrogen in its molecular form is difficult and expensive because it requires employing either extremely high pressures as a gas or very low temperatures as a liquid. Worldwide effort is focused on storage of hydrogen with sufficient efficiency to allow its use in stationary and mobile fueling applications. DOE has set performance targets for on-board automobile storage systems to have densities of 60 mg H$_{2}$/g (gravimetric) and 45 g H$_{2}$/L (volumetric) for year 2010. These are system goals. Metal-organic frameworks (MOFs) have recently been identified as promising adsorbents (physisorption) for H$_{2}$ storage, although little data are available for their adsorption behavior at saturation: a critical parameter for gauging the practicality of any material. This presentation will report adsorption data collected for seven MOF materials at 77 K which leads to saturation at pressures between 25 and 80 bar with uptakes from 2{\%} to 7.5{\%}. Strategies for increasing the adsorption energy of hydrogen in MOFs will also be presented.