Influence of chemical composition of the open bimetallic sites of MOF-74 on H2 adsorption

The success of using physisorbent metal-organic framework materials for hydrogen storage at near-to-room temperatures pass through increasing their adsorption enthalpies. The inclusion of open mixed-metal adsorption sites is one of the most interesting strategies to improve the interaction forces between H-2 and solids. In this work, equimolar mixed metals of Co, Ni, Cu and Zn have been achieved in MOF-74 structure which is known for exhibiting the highest concentration of open metal sites per unit volume among MOF materials. Homogenous distribution of both metals on the solid surface was confirmed in all cases. Textural properties were correlated to the average molecular weight of the unit cell of the samples. Finally, hydrogen adsorption properties were related to the chemical composition of the inorganic clusters in the materials, outstanding the Ni50Co-MOF-74 material with the most effective bimetallic mixture, where high partial charge and polarizability properties synergistically work for enhancing the affinity to hydrogen molecules.