Mechanochemical Dual-Metal Modification of CuBTC Metal-Organic Frameworks for Enhanced Hydrogen Storage

Metal-organic frameworks (MOFs) are promising materials for hydrogen storage due to their high specific surface area and structural tunability. In this study, we provide the first demonstration of enhanced hydrogen storage performance in a CuBTC (also known as HKUST-1) MOF by incorporating nickel and magnesium through a combination of in situ and postmodification solvent-free mechanochemical ball milling. A comprehensive combination of structural and adsorption-desorption characterization is employed to examine and understand the impact of Ni²⁺ and Mg²⁺ divalent metal ions through in situ and postmodification methods. In general, the post-Ni-modification method achieved higher hydrogen storage capacities than in situ-Ni-modification routes. The post-Ni-modified CuBTC with 30 min milling time exhibited the highest hydrogen storage capacity of 4.2 wt % at 20 bar and 77 K, which is 31% higher than the pristine CuBTC. The substitution of Cu²⁺ by Ni²⁺ during the postmodification process increased the active metal sites and Cu⁺ content, thus contributing to enhanced hydrogen storage capacity. Our findings indicate that modification via a solvent-free mechanochemical route is an effective novel strategy for improving the hydrogen storage performance of MOF materials.