Expectedly, the curvature of an adsorption isotherm depends on the chemical composition of the pentanuclear cluster of the framework. The compound ZnCl-MFU-4l exhibits the least curvature and a nearly linear profile in its H2 adsorption isotherms up to 190 bar without plateauing. Such a profile is characteristic of highly porous frameworks without strong H2 adsorption sites. In contrast, the isotherms for Cu I M-MFU-4l frameworks are more curved due to the strong H2 binding to the Cu I sites. Among them, Cu I Zn-MFU-4l reveals the steepest initial H2 uptake.