High quantum yield AIE covalent organic frameworks for sensitive pH monitoring, and copper toxicosis Diagnosis&Remission.

The luminescence properties of covalent organic frameworks (COFs) have attracted significant attention for biomedical applications. However, conventional fluorescent COFs often suffer from weak fluorescence due to aggregation-caused quenching (ACQ), limiting their utility. Given the critical need for highly efficient and sensitive biosensing tools, herein, we propose an aggregation-induced emission (AIE) COF, named COF-Bpy, with the quantum yield up to 25%. Benefiting from the active nitrogen sites within the bipyridine unit, COF-Bpy demonstrates remarkable pH monitoring capabilities across a wide pH range and displays strong coordination affinity towards Cu, achieving satisfactory detection and efficient adsorption of Cu. These properties make COF-Bpy superior in cellular pH imaging, and diagnosis&remission of copper toxicosis at both cellular and nematode levels, as it reduces the late apoptotic cells, improves nematode survival and locomotor states. Additionally, the fluorescence quenching mechanism of dynamic quenching with metal-to-ligand charge transfer is clarified. Briefly, this study not only presents a novel strategy for fabrication of AIE-COFs, but also provides a promising avenue for early diagnosis of pH-related diseases, and offers a theranostics for copper toxicosis management.