(283d) Metal Organic Framework for Hydrogen-Storage Applications

Fuel cell run vehicles sooner or later will be a reality, needs an on-board storage that allows driving range in excess of 400 km, thus requires a tank containing 4 kg of H₂. Since hydrogen is a light weight gas, significant amount of it can be stored in practical size of container only by lowering the temperature to cryogenic temperature (less than 100 K). Thus storage tank filled with solid adsorbents like carbons, zeolites, Metal organic frameworks (MOFs) etc can be a better choice to store same amount of hydrogen but at relatively elevated temperature.

 In this work, we report the hydrogen adsorption properties of four different MOFs namely Zn-BDC, Cr-BDC, Ni-DABCO and Mg-DOBDC. Gravimetric hydrogen adsorption measurements were performed for a wide range of temperature (90 - 298 K) and pressure (0 - 100 bar). At 90-100 K and ~100 bar, all the adsorbents attain saturation which indicates pore filling of adsorbents at this temperature and pressure. On the other hand at room temperature, isotherms are in Henry’s region and metal site unsaturation governs the adsorption. Net adsorption isotherms are obtained because excess or absolute adsorption isotherms do not account the loss of tank volume by adsorbent solid itself. Tank volume calculation shows that the volume required will be ~20 - 30% less with Mg-DOBDC as adsorbent than with empty tank to store similar amount of hydrogen at 100 bar.