Co/Ni mixed-metal sited MOF-74 material as hydrogen adsorbent

The inclusion of Open-Metal Sites (OMS) in MOF materials is one of the most promising routes for increasing the interaction energies between physisorbent materials and hydrogen molecules in order to overcome the gravimetric and volumetric requirements for their application in on-board hydrogen storage. Among materials with OMS, the family MOF-74/CPO-27 is known for exhibiting one of the highest hydrogen surface packing density among adsorbent materials. Previous works reported an increase in the medium-coverage heat of hydrogen adsorption of MOF-74 type materials when metal clusters are built by a Co/Zn mixture. Herein this structure has been successfully synthesized containing Co/Ni mixed-metal clusters in different compositions, and its hydrogen adsorption properties have been also studied. The presence of a certain amount of nickel in Co-MOF-74 enhances the hydrogen adsorption capacity and energy interaction strength of H2 onto this framework, rather than having pure cobalt or nickel clusters, showing the highest adsorption capacity at 77 K and 298 K and Qst when 40% Ni is isomorphically substituted (Ni50Co-MOF-74), confirming that a synergetic effect between both transition metal cations and smaller pore size can contribute to the hydrogen molecules retention in this kind of materials.