Nature 495, 461–466 (2013)

Credit: © 2013 NPG

X-ray crystallography has the overwhelming advantage, compared with other analytical techniques, that it can determine the absolute atomic configuration of a molecule. Its drawback, however, is the need to obtain a crystal and, as a consequence, the isolation of a sufficient amount of the molecule. Now, Makoto Fujita and colleagues report the crystallographic analysis of a diverse range of organic molecules without the formation of crystals and using nanogram to microgram amounts of material. Host–guest interactions within crystalline sponges are exploited to trap small amounts of the molecules within the porous network. This is achieved by placing the crystalline sponge in a solution containing the molecular species and following absorption of the molecules, in an ordered fashion within the pores, X-ray analysis reveals the structure of both the crystalline sponge and molecules (pictured). The structures of aliphatic, aromatic, non-aromatic, polycyclic and chiral molecules — including a marine natural product whose structure has not previously been elucidated — were determined using this technique.