The high-pressure H2 adsorption isotherms of Cu I Mn-MFU-4l and Cu I Cd-MFU-4l were also fitted using a dual-site Langmuir equation to extract the H2 adsorption behavior of the Cu I site (Table ). As shown as solid lines in Figure , simulated H2 isotherms for the stronger adsorption sites (i.e., Cu I sites) for these Cu I M-MFU-4l frameworks at 298 K exhibit steep initial H2 uptake followed by a plateau region. However, Cu I Mn-MFU-4l and Cu I Cd-MFU-4l showed more gently curved simulated isotherms at low pressure and higher saturation pressure than Cu I Zn-MFU-4l.