Furthermore, the porosity of the Cu I M-MFU-4l frameworks was compromised after the Cu Iexchange (Table ), which decreased the contribution from the free H2 in the pore. The framework Cu I Cd-MFU-4l could outperform ZnCl-MFU-4l by 10% in volumetric usable H2 capacity for a 2-35 bar pressure swing at 298 K. At these conditions, the combined contribution from weak physisorption and free H2 in the pore is small relative to that from adsorption at the Cu I sites.