We often say that a substrate fits into its enzyme like a key in a lock, but this metaphor is imperfect. Substrate binding can also change the lock (the structure of the enzyme) to induce a perfect fit. In the journal Angewandte Chemie, an international team of researchers has now introduced a non-biological, crystalline material that demonstrates induced-fit binding behavior when it highly selectively takes up acetylene (C2H2) into its pores.