Mechanochemical Cyclotrimerization: A Versatile Tool to Covalent Organic Frameworks with Tunable Stacking Mode

We introduce the first mechanochemical cyclotrimerization of nitriles, a facile strategy for synthesizing triazine‐containing molecules and materials, overcoming challenges related to carbonization and solubility. Conducting this solid‐state approach in a mixer ball mill with 4‐Methylbenzonitrile, we synthesize Tris(4‐methylphenyl)‐1,3,5‐triazine quantitatively in as little as 90 minutes. Just as fast, this mechanochemical method facilitates the synthesis of the covalent triazine framework CTF‐1 using 1,4 Dicyanobenzene. Material characterization confirms its porous (650 m² g⁻¹) and crystalline nature. Adjusting the induced mechanical energy allows control over the obtained stacking conformation of the resulting CTFs ‐ from a staggered AB arrangement to an eclipsed AA stacking conformation. Finally, a substrate scope demonstrates the versatility of this approach, successfully yielding various CTFs.

This work presents, for the first time, the mechanochemical cyclotrimerization of nitriles. Utilizing Trifluoromethanesulfonic acid and a ball mill, both small molecules and large organic frameworks could be obtained. Screening the reaction of 1,4-Dicyanobenzene by various parameters, such as reaction time, frequency, or temperature, significant impacts on the porosity of the polymer and its crystallinity were revealed.