Growth of single-crystal imine-linked covalent organic frameworks in water using amphiphilic amino-acid derivatives

Abstract Living organisms explored functional biomolecules such as proteins bearing glycine to create single-crystals of minerals in water without resorting to low levels of supersaturation. However, this strategy remains poorly effective in the crystallization of organic polymers. Here, we report a biomimetic strategy and its implementation to synthesize single-crystals of an important class of organic polymers - covalent organic frameworks (COFs) in water under ambient conditions. The strategy explores assemblies of amphiphilic molecules of glycine derivatives as dynamic barriers to separate monomers in water and oil phases, thereby regulating the polymerization and crystallization processes. Monomers first polymerized into disordered solids regardless of concentration variations over five orders of magnitude, then transformed into crystals in a step-by-step fashion with monomers and dimers as main building units, affording six types of single-crystals at the gram-scale with yields of ≥ 92% besides a two-dimensional COF-366. This study will be a valuable addition to the repertoire of crystallization path and methodology of organic polymers and promote their industrial applications.