X-ray single-crystal diffraction, or SCD, is a powerful tool for determining molecular structure but it requires crystals that are often difficult to grow and can require more material than is readily available for exotic compounds. Now, Makoto Fujita of the University of Tokyo and colleagues have found a clever way round these problems. They have used networked porous-metal complexes as a kind of “crystalline sponge” that can hold molecules in an ordered array without their having to form a real stand-alone crystal.
Crystallographic information of such a filled structure can then reveal both the host framework and the guest molecules. The method seems to work amazingly well. Just 5 μg of a rare marine natural product (miyakosyne A) in a zinc-based crystalline sponge was enough for its structure to be determined. The approach should greatly speed up structural determinations for many substances.