  This study employs classical Density Functional Theory (cDFT) to investigate
the adsorption isotherms and structural information of H2 and CH4 fluids inside
MOF-5. The results indicate that the adsorption of both fluids is highly
dependent on the fluid temperature and the shape of the MOF-5 structure.
Specifically, the CH4 molecules exhibit stronger interactions with the MOF-5
framework, resulting in a greater adsorbed quantity compared to H2.
Additionally, the cDFT calculations reveal that the adsorption process is
influenced by the fluid-fluid spatial correlations between the fluid molecules
and the external potential produced by the MOF-5 solid atoms. These findings
are supported by comparison with experimental data of adsorbed amount and the
structure factor of the adsorbed fluid inside the MOF-5. We demonstrate the
importance of choosing the appropriate grid size in calculating the adsorption
isotherm and the fluid structure factors within the MOF-5. Overall, this work
provides valuable insights into the adsorption mechanism of H2 and CH4 in
MOF-5, emphasizing the importance of considering the structural properties of
the adsorbed fluids in MOFs for predicting and designing their gas storage
capacity at different thermodynamic conditions.
