Equi-size nesting of Platonic and Archimedean metal-organic polyhedra into a twin capsid.

Inspired by the structures of virus capsids, chemists have long pursued the synthesis of their artificial molecular counterparts through self-assembly. Building nanoscale hierarchical structures to simulate double-shell virus capsids is believed to be a daunting challenge in supramolecular chemistry. Here, we report a double-shell cage wherein two independent metal-organic polyhedra featuring Platonic and Archimedean solids are nested together. The inner (3.2 nm) and outer (3.3 nm) shells do not follow the traditional "small vs. large" pattern, but are basically of the same size. Furthermore, the assembly of the inner and outer shells is based on supramolecular recognition, a behavior analogous to the assembly principle found in double-shell viruses. These two unique nested characteristics provide a new model for Matryoshka-type assemblies. The inner cage can be isolated individually and proves to be a potential molecular receptor to selectively trap guest molecules.