Covalent organic frameworks (COFs) are an emergent class of polymeric materials defined by their crystallinity, permanent porosity, and modularity. By varying the identity of monomeric components, these materials’ structure and function can rationally be designed for use as chemical sensors, photovoltaics, photocatalysts and more. However, implementation of these materials into devices has faced limited success due to their low quality, polycrystalline nature; these materials had not achieved their desired crystalline structure due to small domains aggregated in random orientations to each other. Expanding on an earlier study in which single crystalline two-dimensional COFs as solution stable colloids were synthesized, we perform high quality optical characterization via ultrafast spectroscopy. Exciton dynamics of COFs are examined via a power dependent transient absorption study of COF-5. By performing transient absorption in the high fluence regime, exciton-exciton annihilation kinetics were investigated to determine exciton diffusion lengths. Comparing exciton-exciton annihilation kinetics across a number of different sizes of COF-5 colloids revealed a crystallite size dependence to exciton-exciton annihilation dynamics, unveiling the effect of colloid domain size on excitonic transport in these materials.

Exciton dynamics in colloidal covalent organic frameworks

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.