Hydrogen cryo-adsorption by hexagonal prism monoliths of MIL-101

Hexagonal prism shaped monoliths of envelope density 0.40–0.467 g/cm3 and remarkable mechanical stability were obtained from MIL-101 powder. The hydrogen adsorption isotherms within an extended pressure range show that the excess adsorption decreases with the increasing density of the pellets. At 77 K and 150 bar, the total volumetric capacity is 46.5 g/L; the discharge to 159 K and 5 bar leads to 45 g/L (38.8 g/L referring to the outer tank volume) supporting MIL-101 as a promising candidate for applications in the 77–160 K range of interest for cryo-adsorption hydrogen storage method. The isosteric adsorption enthalpy evaluated from the experimental data with the vanʹt Hoff equation, using fugacity, is in agreement with the calorimetric heat of adsorption reported in literature. Monoliths of this shape allow the best possible packing density of any sorbent in a container and the primary data reported here on MIL-101 could serve as material engineering properties required for modeling hydrogen storage tanks.