This paper also shows that the double cluster requires elevated temperatures to form. Compared with studies which did not show any interconversion between pre-synthesised single and double molecular clusters at room temperature, our observation demonstrates that double clusters can form from single clusters, but that that elevated temperatures are necessary. This is in keeping with our earlier work showing that the hcp UiO-67(Hf) framework, containing the double cluster, requires a higher temperature to form compared to fcu framework. In this work, we chose to examine the behaviour of our reaction mixtures at two elevated temperatures: 150°C and 120°C. By carrying out the reactions at a lower temperature, any kinetically limited processes -such as hydrolysis reactions -should be slowed down. In both reactions carried out at 120°C, growth of all peaks, especially the intra-cluster peaks, was significantly slower than at 150°C (the 3.5, 4.9 and 9.2 Å peaks reached their maximum at 22.4, 29.5 and 26.3 minutes respectively for the no-BDC reaction at 120°C, compared to 10.1, 9.3 and 11.3 minutes for the no-BDC reaction at 150°C [Table ]), suggesting that these cluster reactions (including the formation of the double cluster from single clusters) are indeed kinetically limited.