In situ XRPD measurements showed that humidification of Ni(PyC) 2 results in transformation to the known non-porous hydrate phase (a new crystal structure phase that incorporates water into the framework) Ni(PyC) 2 (H 2 O) 4 [ ] (see Sec. S ). We observed a similar transformation for Ni(PyC-m-NH 2 ) 2 at high humidification. After one day storage at % RH and room temperature, Ni(PyCm-NH 2 ) 2 converted to the pure hydrated phase. We determined the new structure as Ni(PyC-m-NH 2 ) 2 (H 2 O) 4 , isomorphous with Ni(PyC) 2 (H 2 O) 4 , but with an expanded unit cell to accommodate the amino groups ( . Å 3 vs. . Å 3 ). In this case, the water ligands and the amino groups coordinating Ni both appear to form a hydrogen bonding network with neighboring carboxylates. See Sec. S for detailed methods. Tab. displays the Henry coefficients and selectivities at dilute conditions, which follow from the ratio of the Henry coefficients. Indeed, Ni(PyC-m-NH 2 ) 2 exhibits a higher Xe Henry coefficient and Xe/Kr selectivity than the parent Ni(PyC) 2 . For comparison, we also include in Tab. the benchmark material SBMOF-, which Ni(PyC-m-NH 2 ) 2 also out-performs for Xe/Kr separations. Ni(PyC-m-NH 2 ) 2 also has a greater Ar Henry coefficient than the parent MOF. 2 also shows changes due to solvent removal after activation, but is relatively unchanged after exposure to air for two weeks.