To gain further insights, we performed in situ XRPD measurements during the activation and humidification processes of the as-synthesized powders of Ni(PyC) 2 and Ni(PyC-m-NH 2 ) 2 at beamline -ID-(XPD) at the National Synchrotron Light Source II (see S ). The as-synthesized powders both were mixtures of solvent-filled MOF and hydrate phase, though Ni(PyC-m-NH 2 ) 2 contained signifi-cantly less hydrate phase. Under the conditions of this experiment, the activation procedure successfully transformed all hydrate phase and removed all solvent from Ni(PyC) 2 , resulting in activated Ni(PyC) 2 (published with space group symmetry P nn2 [ ]). Further humidification resulted in rapid and complete transformation to the hydrate phase, equilibrating after roughly min. For Ni(PyCm-NH 2 ) 2 , activation successfully transformed the hydrate, but did not remove all solvent from the as-synthesized sample. The humidification process then resulted in a partial transformation to a : mixture of pore-filled anhydrate to hydrate phase. Ni(PyC-m-NH 2 ) 2 was more resistant to hydration, converting to the hydrate phase more slowly and not reaching full conversion after min. We could not completely rule out the possibility that remaining solvent in Ni(PyC-m-NH 2 ) 2 may have hindered the subsequent hydration processes. N.b., for some samples used for lab-and synchrotron-measured patterns of the parent Ni(PyC) 2 (but not Ni(PyC-m-NH 2 ) 2 ), we observed extra low angle reflections with d-spacings of " . , . , and . Å. These could not be identified using the software Match v.3.9.0 [ ] to search the International Centre for Diffraction Data (ICDD) powder diffraction database nor through a search of reasonable structures of precursors and building units in the Inorganic Crystal Structure Database (ICSD) and Cambridge Crystallographic Data Centre (CCDC) database . Since the peaks do not appear to change significantly during the processing steps, and were not observed in all batches from separate syntheses, we suspect that they may come from an unknown impurity phase, which does not partake significantly in the moisture or gas uptake.