Host‐Guest Chemistry in a Capillary Applied to the Facilitation of the Crystalline Sponge Method

Abstract Capillary is a handy tool for transferring, mixing, and storing small volumes of liquid. Here, we show that the stepwise dipping of host and guest solutions into a capillary allows efficient preparation, crystallization, and X‐ray analysis of various host–guest complexes. The crystals formed in capillaries are comparable in quality to those grown in regular flasks and subjected to X‐ray analysis without being removed from the capillary. We further apply the capillary technique to the crystalline sponge method, a practical domain of host–guest chemistry, successfully overcoming several technical issues.