Accessing High-Nuclearity Cluster-Based Metal−Organic Frameworks Using Early Lanthanoids: A Study of RE-UiO-66

There are very few examples in the literature of rare-earth metal−organic frameworks (RE-MOFs) containing high-nuclearity clusters (RE 6 or higher) using La(III), Ce(III), Pr(III), and Nd(III). The few examples of early lanthanoid cluster-based MOFs that do exist have not been completely characterized, reflecting the difficulty in obtaining these MOFs as phase pure bulk microcrystalline powders. To understand and overcome this limitation, we identified a competing reaction that leads to REF 3 and then tuned the synthetic conditions to suppress REF 3 formation and favor the formation of the MOF. Using this approach, we obtained six analogues of RE-UiO-66 as phase pure microcrystalline powders using Ce(III), Pr(III), and Nd(III) for the first time. These materials are thoroughly characterized, and this study provides insight into the synthesis of early-lanthanoid cluster-based MOFs.