Conversion of Soluble Polyimines to Covalent Organic Framework Films and Composites

Covalent organic frameworks (COFs) have been demonstrated for promising applications across research areas and industries. As research in the field advances, there is an increasing need for processing techniques for printing and fabricating COFs, as well as for synthesizing COF composites for advanced materials. To achieve this goal, a versatile approach allowing the synthesis of COFs through polyimines has been developed. Specifically, linear polyimines derived from an aliphatic diamine and aryl dialdehydes were synthesized and subjected to exchange reactions with various vertex amines to generate high-crystallinity imine-based COFs. These polyimines, also referred to as Schiff base polymers, are soluble in organic solvents, enabling solution-based processing and printing with vertex amines to create films of the desired shapes. Highly crystalline COF films were then fabricated by converting precursor films through vapor annealing. This process enables the fabrication of COFs on both microscopic and macroscopic scales. Furthermore, this method provides a straightforward approach to creating advanced functional materials, such as COF/CNT nanocomposites.