Modulator-Enhanced Synthesis of Isoreticular Pyridine-Based, Imine-Linked Covalent Organic Frameworks (COFs)

Dynamic covalent chemistry (DCvC) has revolutionized the design of crystalline materials, particularly reticulate structures such as covalent organic frameworks (COFs), by enabling error-correcting assembly processes. COFs, with their structural precision and functional diversity, represent an emerging class of porous, crystalline materials with diverse applications. Herein, we report the synthesis of a novel family of crystalline, imine-linked COFs derived from a pyridine-based aldehyde scaffold. By employing aniline as a reversible modulator, precise control over the framework formation kinetics could be achieved through reversible imine exchange, thus facilitating optimal error correction and crystal growth. This strategy yielded three isoreticular COFs with distinctive crystallinity, tunable pore architectures, and high surface areas (up to 2829 m²/g). These frameworks also exhibited remarkable thermal stability (up to 485 °C) due to the synergistic effects of the rigid pyridine core and the resonance-stabilized imine linkages. These pyridine-based COFs, featuring nitrogen-rich structures and intrinsic coordination versatility, provide a unique platform for advanced functionalities driven by the pyridine-rich environment throughout the frameworks. By leveraging an underexplored aldehyde-functionalized pyridine building block, this work advances the design scope of COFs beyond traditional benzene-centered COFs. The high crystallinity, remarkable surface areas, thermal stability, and coordinating pyridine sites make these COFs well-suited for environmental remediation, gas capture, and energy applications.