One-Pot Hierarchical Assembly of Simple Molecules to Vinylene- and Indole-Linked Covalent Organic Frameworks

Abstract The development in the synthesis of covalent organic frameworks (COFs) has been oriented toward the integration of simplicity, accessibility, stability, diversity, and functionality. However, a central bottleneck remains the lack of effective strategies for assembling simple, unsymmetric, and readily available molecules into highly ordered frameworks. Here, we report a practical synthesis of robust, diversified, and functional COFs via one-pot assembly from a low-cost and simple-structured molecule, 4-methyl-3-nitrobenzonitrile (MNBN). Leveraging the versatile but orthogonal reactivities of MNBN, a three-step cascade sequence, including nitrile cyclotrimerization, Knoevenagel condensation, and reductive cyclization, achieved the symmetrization, reticulation, and functionalization in one pot, thereby enabling the hierarchical construction of two series of COFs with stable o-nitrostyrene or indole linkages. The resulting COFs displayed high crystallinity, permanent porosity, and exceptional stability; solid-state nuclear magnetic resonance (SSNMR) experiments combined with selective isotopic-labeling synthesis further confirmed the high selectivity and controllability of the hierarchical assembly. Notably, the indole-linked COFs, featuring conjugated and electron-rich frameworks, displayed emergent photoelectronic properties and served as efficient, reusable catalysts in both metal-free photocatalytic and metallaphotoredox reactions. By hierarchically exploiting the intrinsic reactivity of a simple, unsymmetric molecule, this work bridges classical organic synthesis and cross-scale covalent assembly, achieving the programmable construction of stable, diversified, and functional COFs.