Studies on Zr and Hf clusters to track or solve their structures are not straightforward (especially in situ studies of solvothermal syntheses). Bragg diffraction cannot be used to study the critical non-crystalline species. Solution NMR is extremely challenging, as the key nuclei ( 17 O, Zr, Hf and 179 Hf, in the absence of organic linker species ) all either have large quadrupolar moments (e.g. Q( 177 Hf) = 4.9 b), have low gyromagnetic ratios (e.g. γ( 179 Hf) = -0.682x10 7 rad/Ts), or are of very low abundance (e.g. 17 O = 0.038 %). While extended X-ray absorption fine structure (EXAFS) methods can identify Zr and Hf species in solution, and are sensitive to species with low abundance, this technique is limited to smaller molecular clusters such as the tetramer and single cluster, due to multiple scattering events reducing the sensitivity required to observe longer-range coordination, such as that seen in the molecular double cluster or in the interlinked MOF.