Postsynthetic N-methylation making a metal-organic framework responsive to alkylamines.

The postsynthetically created electron-deficient 2,2'-bipyridinium moieties in a Zr-MOF provide charge-transfer interacting sites for recognizing and capturing alkylamines with excellent selectivity; meanwhile the MOF shows fast and reversible vapochromism and luminescence quenching in response to alkyamines.