Aqueous synthesis of highly crystalline acylhydrazone COFs

The central feature of covalent organic frameworks (COFs) is crystallinity which is conducive to forming a uniform pore structure. However, synthesis of highly crystalline COFs based on stable covalent bonds remains formidable task. In this paper, a highly crystalline acylhydrazone COF-BD was synthesized in aqueous phase. The synthesis mechanism was proposed that the protonated hydrazide monomers dissolved in aqueous phase reacted with aldehyde monomers by deprotonation into the micellar. By investigating the effects of experimental parameters on the crystallinity of COF-BD, it was founded that under C9–COONa as surfactant, 80 °C, and 1.0 eq acetic acid as catalyst, acylhydrazone COF-BD with good crystallinity could be prepared. To prove the extensibility of this method, another acylhydrazone COF was prepared successfully. [Display omitted] •The aqueous synthesis of a highly crystalline 2D COF based on acylhydrazone bonds was presented.•The reaction mechanism of acylhydrazone COF was elaborated.•The influence of surfactant, temperature, and catalysis on improving crystallinity were investigated systematically.•The extensibility of acylhydrazone COF synthesis was explored.