(627g) Modeling the Nucleation and Growth of Covalent Organic Frameworks: Size Distributions and Aspect Ratios

Covalent organic frameworks (COFs) are multilayered porous materials that form through reactions between molecular precursors. We model the kinetics using second-order primary nucleation, templated nucleation of additional layers, and first-order lateral growth of COF particles. The model consists of a species balance equation for the reversibly reacting precursors and a population balance model for the COF particles with variable diameters and thickness/number of layers. The method of moments was used to solve the equations, giving analytic expressions for the total concentration of COF particles, the average number of layers (thickness), the average COF particle diameter, and the COF material yield as a function of time. The model predicts how rate parameters for primary nucleation, templated nucleation, and lateral growth influence the COFs yield, particle size, and aspect ratio. We demonstrate that the model can also be used to fit experimental data and extract rate parameters. Our findings reveal that determining the complete set of rate parameters requires information about particle aspect ratio, beyond yield vs. time as reported in prior studies.