Hydrogen Storage in New Metal-Organic Frameworks

Five new metal-organic frameworks (MOFs, termed MOF-324, 325, 326 and IRMOF-61 and 62) of either short linkers (pyrazolecarboxylate and pyrazaboledicarboxylate) or long and thin alkyne functionalities (ethynyldibenzoate and butadiynedibenzoate) were prepared to examine their impact on hydrogen storage in MOFs. These compounds were characterized by single-crystal X-ray diffraction, and their low-pressure and high-pressure hydrogen uptake properties were investigated. In particular, volumetric excess H-2 uptake by MOF-324 and IRMOF-62 outperforms MOF-177 up to 30 bar. Inelastic neutron-scattering studies for MOF-324 also revealed strong interactions between the organic links and hydrogen, in contrast to MOF-5 where the interactions between the Zn4O unit and hydrogen are the strongest. These data also show that smaller pores and polarized linkers in MOFs are indeed advantageous for hydrogen storage.