Controlled growth of covalent organic frameworks (COFs) is critical to understand the underlying crystallization mechanism but challenging to achieve. While single crystalline COFs have been prepared in many cases, the isolation and characterization of the intermediate phases face less successes. In this work, by utilizing a sterically hindered organic Lewis acid catalyst, tris(pentafluorophenyl)borane, we achieved the preparation of both the final framework and the oligomer intermediate single crystal of COF-300, under carefully controlled solvothermal conditions. The distinct reaction pathways were studied in detail using SEM and PXRD analysis. The results unambiguously revealed the first evolution of the oligomer intermediate phase and its gradual transformation to the final framework. Our findings complement the mechanistic studies on COF growth and offer a new design approach for the kinetic and thermodynamic control in COF formation.
https://doi.org/10.1039/d6cc02265k
