Giant Five-Shell Polyoxometalate Cages and the Single-Cluster-Based Nanowire Superstructures.

The preparation of polyoxometalate molecular cages has always been a long-term and challenging pursuit. In this work, we have successfully prepared two unprecedented giant heterogeneous POM-based purely inorganic molecular cages with symmetry, which contain the aggregation of M (M = Ni, Co)-substituted trilacunary {PW} and Mn-bridged {W}. Sodium ions are used as templates to fill the cages. The polyanions of cages can be represented as {Na(MnO)(WO)[MnO(OH)](PWNiOH)} and {Na(MnO)(WO)[MnO(OH)](PWCoOH)}. The entire structure can also be considered as a five-shell Na@Mn@{W}@Mn@{PWM} arrangement. The electrostatic effects of sodium ions within the cages enhance the stability of the structures, allowing them to maintain a monodisperse and stable state in aqueous solutions. Interestingly, the cages assemble into nanowires through electrostatic contact with the cationic CTA ligand, demonstrating its flexible assembly capability at the single-cluster level. This giant POM inorganic molecular cage holds significant potential for application in the preparation of functional nanomaterials.