We initially observed the behaviour of our HfCl4 metal salt in water alone as a baseline, since the behaviour of ZrCl4 in water is well-established. We then focussed on a 65:25:10 (by volume) DMF : formic acid : water mixture (referred to below as "DFW 65:25:10") as a solvent, setting out to elucidate the behaviour of the UiO-related system throughout the reaction at different temperatures. We also investigated whether the stages and rate of cluster formation are affected by the presence of additional coordinating linkers, and explored the timing of the framework growth and crystallinity relative to the cluster formation, by performing reactions at the two different temperatures both with and without terephthalic acid (H2BDC) linker, i.e. reactions with the potential to form UiO-66-type structures (containing BDC, at 150 and 120°C), and molecularcluster-only reactions (no BDC, at 150 and 120°C) [Table ]. We start by detailing our approach to model the different clusters present, beginning with the aqueous solution of HfCl4. We then consider the effect of changing the solvent and temperature, and the effect of adding linkers, on the type and evolution of the clusters in these UiO-related systems.