Grafting bimetallic active sites to MOFs via covalent attachment to the ligand strut is a particularly appealing approach (Fig. ), as it not only provides a robust connection to the framework surface but can also be adapted to diverse ligand environments, metal precursors, and pore structures. For example, aminefunctionalized frameworks have been used to attach salicylidene, 15 iminopyridine, and NNN-pincer complexes to pore walls, as well as iminocatecholate-bound Ru(II) metathesis catalysts (Fig. ). Furthermore, amine groups are readily incorporated into many common MOF structure types. However, while postsynthetic covalent grafting offers a large selection of possible ligand and pore environments, an unresolved challenge is controlling the active site nuclearity. Grafting at low surface coverages results in predominantly mononuclear sites, while higher loadings risk the formation of larger nuclearity clusters (Fig. ).