This further suggests that, by adjusting the temperature of the reaction to take advantage of the different rates of cluster condensation and of framework growth, it may be possible to allow more time for the clusters to join together prior to coordination by inter-cluster linkers, and so obtain "multi-cluster" species intermediate between the double cluster and previously-observed infinite 1-D chains, all based on the M6 single cluster unit. Alongside the previous studies, our work with formic acid corroborates that cluster formation in these UiO systems is determined by a complex interplay of temperature, ageing, concentration of metal salt and the type, concentration and pH of acid (which can act as a modulator and as directing groups ). The complex processes discussed in this work motivate further exploration to enable understanding in greater detail, and hence improved exploitation. With careful control over the timing of linker addition, and consideration of the coordination-site-preferential exchange between linkers and terminating ligands known to occur with molecular double clusters (particularly involving the ligands at the "narrow" ends of the cluster), this enhanced understanding of cluster formation in UiO systems could lead to intentional control of the framework growth, potentially providing routes to ordered mixed-linker frameworks, double-cluster-containing nanosheets such as those we previously reported, or as-yet-unknown "multi-cluster" MOFs.