Coordination-templated construction of single-crystal covalent organic frameworks

Abstract

Covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) are sought for their tunable porous structures and potential utility. Whereas the coordination bonds in MOFs enable the generation of single crystals, facilitating insight into structure-function relationships, this is not typically the case for COFs. Here, we present a simple and rapid synthetic method that exploits coordination-directed imine formation to prepare families of highly crystalline porous materials that are MOF-COF (MOCOF) hybrids. This synthetic approach consistently provides 14 high-quality single crystals formed using various combinations of imine (COF) and N-donor linker ligand (MOF) within 1 to 2 days, with sizes ranging from 50 to 500 μm, allowing determination of the single-crystal X-ray structures. These crystal structures provide insight into architectures, structural evolution, and host-guest interactions (including chirality recognition) with atomic resolution. Moreover, these MOCOF hybrids can be deconstructed through linker ligand removal and exfoliated to form ultrathin COF nanosheets.