Boosting the Brightness of Covalent Organic Frameworks by Integration of Dual-Docking Luminogens with Aggregation-Induced Emission Effect

Most covalent organic frameworks (COFs) exhibit minimal or weak emission, even when constructed with highly emissive AIEgens. The fluorescence quenching issues in COFs are typically attributed to nonradiative decay induced by molecular motion or intramolecular charge transfer. As a result, designing emissive COF materials remains a desirable yet challenging task. In this study, we present the construction of highly emissive COFs through the integration of dual-docking AIEgens. Mechanism studies reveal that this integration effectively restricts undesired molecular motion and reduces charge transfer to the imine linkage, thereby enhancing fluorescence generation and improving the crystallinity of the COFs. One benzothiadiazide-based COF, COF-DPQP-BT, exhibits notable brightness with a photoluminescence quantum yield of 36.5% and is successfully utilized for in vivo three-photon fluorescence imaging of brain vasculature in mice, achieving an imaging depth of approximately 1.2 mm. This work provides valuable insights for the design of emissive COFs.