Geomimetic Interfacial Hydrothermal Synthesis of Crystalline Ionic Vinylene‐Linked Covalent Organic Frameworks

Abstract Ionic vinylene‐linked covalent organic frameworks (ivCOFs) with ionic characteristics and highly conjugated structures have been promising functional materials. However, both the number of reported ionic vinylene‐linked COFs and its synthetic methodologies still be limited. Herein, two new kinds of ionic vinylene‐linked covalent organic frameworks (named as COF‐NUC‐1 and COF‐NUC‐2) are synthesized by novel geomimetic interfacial hydrothermal synthesis for the first time. Due to the insolubility of conjugated aldehyde monomers in water, a molecule/water interface is created, where the water‐soluble N‐ethyl‐2,4,6‐trimethylpyridinium bromide (ETMP‐Br) can react with aldehyde monomers via the interface‐confined Knoevenagel condensation reaction. The resultant ionic COFs show high crystallinity, high chemical stability, and hydrophilic nature. Benefiting from electron‐withdrawing and redox properties of pyridinium salts, the as‐fabricated memristor based on COF‐NUC‐1 film shows stable nonvolatile memory effects, featuring a high ON/OFF current ratio of 0.66 × 10 3 and a small switch‐on voltage of −0.68 V. This work expands the realm of ivCOFs and deepens the understanding of hydrothermal synthesis.