A supramolecular lanthanide separation approach based on multivalent cooperative enhancement of metal ion selectivity.

Multivalent cooperativity plays an important role in the supramolecular self-assembly process. Herein, we report a remarkable cooperative enhancement of both structural integrity and metal ion selectivity on metal-organic ML tetrahedral cages self-assembled from a tris-tridentate ligand (L) with a variety of metal ions spanning across the periodic table, including alkaline earth (Ca), transition (Cd), and all the lanthanide (Ln) metal ions. All these ML cages are stable to excess metal ions and ligands, which is in sharp contrast with the tridentate (L) ligand and bis-tridentate (L) ligand bearing the same coordination motif as L.