leading to a final composition Fe [Fe II (CN) 6 ] 3 • 14 H 2 O. A second composition, M 3 [M III (CN) 6 ] 2 • xH 2 O, containing M III (CN) vacancies also commonly occurs in PBAs. These hexacyanometallate vacancies produce large voids which are filled with water clusters in the as-synthesised materials. Both the vacancies and the water clusters play a critical role in determining the functional properties of these frameworks, including their mechanical robustness , their stability as pigments and whether they show photomagnetism . In addition, the ordering in space of these defects will likely play a key role in mass transport through these materials for applications including ionic conduction and gas sorption. PBAs also demonstrate one of the significant challenges of studying defective hybrid frameworks: it can be extremely difficult to determine their structures. Although dozens of compositions of PBAs have been reported, they are typically produced as microcrystalline powders, which inherently limits the amount of information available through diffraction. Even for single crystal and total scattering studies where information about the correlation of vacancies through the lattice can be obtained, the high symmetry of the parent structure means the local defect-structure determined through crystallography is superimposed on both the non-defective structure and the symmetryrelated transformations of the defect, hindering detailed interpretation. The presence of disorder also complicates the interpretation of spectroscopic data, as deconvolution of different defect sites can often be challenging unless there are additional helpful features such as moderate paramagnetism . These problems are by no means unique to PBAs 9 and thus, despite the utility of accurate representations of defect-structures, we are often forced to resort to simplified models which omit the true complexity of defective molecular frameworks.