A self-assembling cube that can pack away massive aromatic guests such as coronene and fullerenes from the surrounding solution is being reported by chemist Jonathan R. Nitschke and colleagues at the University of Cambridge (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201100193). The supramolecular cage has six walls, each composed of a modified porphyrin. The cubic cage’s eight corners are demarcated by eight iron atoms, which are held in place by ligands affixed to the porphyrin walls. Nitschke says this is the first cubic cage big enough to completely sequester large aromatic guests from the environment. Because the cage walls’ π-electron density sequesters C70 better than the more curved C60 incarnation, Nitschke says the cages could be useful for encapsulating or separating higher fullerenes from fullerene soot. He also sees applications in keeping reactive molecules or drugs sequestered until an appropriate signal permits their release. Next up, Nitschke says he hopes to do some metalloporphyrin-catalyzed chemistry in the caged environment that could be varied depending on which metals were placed into the porphyrin scaffold.