Quantitative Description of the Lateral Growth of Two-Dimensional Covalent Organic Frameworks Reveals Self-Templation Effects

Quantitative mechanistic insight into polymerizations that produce highly crystalline two-dimensional covalent organic frameworks (2D COFs) is a prerequisite for their controlled synthesis. However, developing quantitative models for COF formation is challenging since a plethora of molecular species and reactive pathways must be considered simultaneously. Here, we demonstrate an approach to develop an analytical relationship between 2D COF lateral (in-plane) growth rates and fundamental microscopic processes, based on a previously reported kinetic Monte Carlo model. The bond formation rate, the relative bond formation rates at crystal faces and edges, and the lattice size are all found to be critical parameters for the determination of the lateral growth rates. Our analysis also reveals the importance of self-templation in 2D COF growth, which provides a unified understanding of supramolecular interactions in 2D polymerization. Our analytical model represents an important step toward a generalized mechanistic understanding of 2D COF formation. Also, the quantitative description provided here opens the way to monomer design and polymerization conditions that favor lateral growth.