A sustainable ultramicroporous MOF for hydrogen storage (Poster)

Hydrogen storage remains a critical challenge in the transition toward sustainable energy systems. Metal-organic frameworks (MOFs) have emerged as promising materials due to their tunable porosity and chemical versatility.1 While large-pore MOFs offer high hydrogen storage capacities and frameworks with open metal sites provide strong H2 interactions, ultramicroporous MOFs remain relatively underexplored despite their potential for enhanced hydrogen confinement effects.2 Here, we present magnesium gallate as a sustainable lightweight ultramicroporous candidate for hydrogen storage. The activation of the MOF was investigated using in situ synchrotron X-ray diffraction, while hydrogen storage was characterized via physisorption and in situ neutron diffraction D2 sorption experiments. The results reveal exceptionally strong interactions with hydrogen at 77 K, achieving full site occupancy at extremely low pressures (below 6 bar). Physisorption experiments and neutron diffraction consistently indicate full occupation of all adsorption sites, corresponding to 4 D2 molecules per 3 metal sites. Interestingly, this strong interaction does not arise from Kubas-type interactions with the metal centres, but is attributed solely to the confinement effects within the ultramicropores. These findings demonstrate the potential of ultramicroporous MOFs for efficient hydrogen storage, offering a complementary approach to existing strategies focused on large-pore systems and open metal sites.