Combination of Knoevenagel Polycondensation and Water‐Assisted Dynamic Michael‐Addition‐Elimination for the Synthesis of Vinylene‐Linked 2D Covalent Organic Frameworks

Vinylene-linked two-dimensional conjugated covalent organic frameworks (V-2D-COFs), belonging to the class of polymers, have attracted increasing attention due their extended π-conjugation over 2D backbones associated with high chemical stability. The Knoevenagel polycondensation has been demonstrated as a robust synthetic method provide cyano (CN)-substituted V-2D-COFs unique optoelectronic, magnetic, and redox properties. Despite successful synthesis, it remains elusive for relevant polymerization mechanism, which leads relatively low crystallinity poor reproducibility. In this work, we demonstrate novel synthesis CN-substituted via combination water-assisted dynamic Michael-addition-elimination, abbreviated KMAE polymerization. existence C=C bond exchange between two diphenylacrylonitriles (M1 M6) is firstly confirmed in situ high-temperature NMR spectroscopy study model reactions. Notably, intermediate M4 synthesized Michael-addition can proceed Michael-elimination quantitatively, leading an efficient exchange, unambiguously confirming nature Michael-addition-elimination. Furthermore, addition water significantly promote reaction rate Michael-addition-elimination highly within 5 mins. As result, provides strategy crystallinity, by four examples V-2D-COF-TFPB-PDAN, V-2D-COF-TFPT-PDAN, V-2D-COF-TFPB-BDAN, V-2D-COF-HATN-BDAN, based on simulated experimental powder X-ray diffraction (PXRD) patterns well N2-adsorption–desorption measurements. Moreover, high-resolution transmission electron microscopy (HR-TEM) analysis shows crystalline domain sizes ranging from 20 100 nm newly V-2D-COFs.