Enhanced Hydrogen Storage in Metal Organic Framework/Graphene Oxide Composites: Experimental Characterization and...

Metal-organic frameworks (MOFs) constitute a rapidly expanding class of microporous materials. In recent years, numerous MOFs with tunable nanoporous architectures have been developed as promising candidates for natural gas and hydrogen storage. To enhance the hydrogen storage capacity of MOFs while reducing the overall cost, this study integrates MOFs with cost-effective materials that provide additional active sites for hydrogen adsorption. Here, we report the development of a composite consisting of graphene oxide (GO) and Ni-based MOF-74 (Ni-MOF-74), which combines the high surface area and functional groups of GO with the extensive porosity and open metal sites of the MOF. The Ni-MOF-74/GO composite was synthesized via an in situ growth method and extensively characterized by using transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller surface area analysis to confirm its integrated structure and porosity. Hydrogen adsorption isotherms at 77 K and up to 1 bar reveal that the Ni-MOF-74/GO composite exhibits a significantly higher H₂ uptake capacity than either pristine GO or Ni-MOF-74 alone. Notably, the composite with an optimal GO loading (10 wt %) achieves the highest storage enhancement, demonstrating a synergistic effect between GO and the MOF in maximizing hydrogen adsorption. Density functional theory (DFT) and Monte Carlo simulations provided molecular-level insights, indicating that H₂ molecules occupy both the microporous channels of Ni-MOF-74 and the GO surface, particularly at the Ni-MOF-74/GO interfacial regions. This hybrid framework exhibits a slightly stronger hydrogen adsorption energy (-3.34 kcal/mol) compared to Ni-MOF-74 alone (-3.25 kcal/mol), with minimal structural distortion upon H₂ uptake.