Diffraction patterns were collected under various temperatures and gas atmosphere conditions and Rietveld refinements were conducted to examine the structures of activated and D2dosed Cu I Mn-MFU-4l under various conditions. Full refinement procedures are presented in the SI, while selected structural parameters are summarized in Tables and. We . Schematic illustration of D2 adsorption sites in Cu I Mn-MFU-4l refined against powder neutron diffraction patterns collected at 7 K for various cooling and heating cycles. Brown, blue, grey, emerald green, and light green spheres represent Cu, N, C, Mn, and Cl atoms, respectively, whereas orange and yellow spheres represent centroids of D2 for site I and site II, respectively, as refined with the super atom approach. Powder Synchrotron X-Ray Diffraction. Since we were not able to obtain in situ D2dosing powder neutron diffraction data for Cu I Cd-MFU-4l, we investigated whether a structural change is observed upon H2 dosing for Cu I Cd-MFU-4l by in situ H2-dosing powder x-ray diffraction with synchrotron radiation. The sample was activated under dynamic vacuum at 373 K prior to collecting diffraction patterns at 153 K on the activated framework. Subsequently, H2 was dosed to approximately 140 mbar at equilibration to ensure the saturation of Cu I sites with H2. The Rietveld refinements against the diffraction patterns of the activated and H2-dosed Cu I Cd-MFU-4l show a decrease in the unit cell parameter by 0.095(1) Å from 31.677(1) to 31.5825 (7) Å. This magnitude of contraction is similar to the powder neutron diffraction results for Cu I Mn-MFU-4l