Enhancing exciton delocalization and energy transport in organic materials through tethered covalent organic frameworks

The ability to tune electron-phonon coupling and control exciton delocalization in organic materials is crucial for advancing energy transport technologies, including solar energy conversion and excitonic circuits. Prior research has demonstrated that tethering non-covalent dye assemblies significantly enhances exciton delocalization by minimizing intermolecular vibrations, restricting conformational freedom, and enforcing precise spatial orientation of the monomers. While this approach improves the electronic coupling in the traditionally self-assembly noncovalent systems, the intrinsic structural fragility of the tethered supramolecular polymers driven by - interaction and the continuous monomer exchange and reorganization of the monomer units introduces structural heterogeneity, which engenders exciton decoherence and limit energy migration efficiency in organic materials. To overcome this challenge, we integrated tethering technology into a covalent organic framework which possessed a more robust, ordered tunable framework, and subsequently cleaved the linkers to isolate highly ordered domain template that enhanced strong exciton delocalization to curb the challenge of continuous exchange of building blocks and reorganization to reach energy minimums. To achieve this post covalent modification, we adapted established supramolecular tethering methods to COFs by using porphyrin-based frameworks, then cleaved linkages and developed purification techniques for the highly hierarchical tethered porphyrin nanostructures, which were characterized with FTIR, SEM, PXRD and B-E-T Surface Analysis. These techniques was used to characterize COF solid-state morphologies, elucidate chemical structure, bonding and pore size volume respectively. Additionally advanced time-resolved electronic and vibrational spectroscopies, including ultrafast transient absorption (TA) spectroscopy and femtosecond stimulated Raman spectroscopy (FSRS), were required to probe the excitonic properties of the tethered structures from the framework. This approach will provide a clear understanding of how structural rigidity and intermolecular vibrations influence exciton transport, free from the confounding effects of continuous exchange and reorganization that plague traditional supramolecular polymers and deliver highly ordered domain that foster an efficient intra or inter-assembly energy migration.