An AIEgen‐Based Covalent Organic Polymer With NIR‐II Emission for 980 nm Excitable Tumor Phototheranostics

ABSTRACT Covalent organic porous polymers (COPs) represent an attractive platform for phototheranostics due to their structural tunability and extended conjugation. Nevertheless, achieving COPs that simultaneously exhibit efficient second near‐infrared (NIR‐II) fluorescence and long‐wavelength excitation remains a considerable challenge, limiting their applicability in deep‐tissue theranostics. In this study, we constructed a conjugated COP (BTTB‐PA) by integrating an aggregation‐induced emission luminogen (AIEgen) BTTB into a rigid imine‐linked framework. The confined environment within BTTB‐PA skeleton restricted molecular motion of the AIEgen, activating intense NIR‐II fluorescence. To further enhance photophysical properties, the dynamic imine bonds in BTTB‐PA were converted into planar thiazole linkages through post‐synthetic modification, yielding BTTB‐PSH with improved structural rigidity and conjugation. This transformation resulted in a pronounced prolong in absorption and exceptional photothermal conversion efficiency under 980 nm laser irradiation. As a result, BTTB‐PSH nanoparticles enabled high‐contrast NIR‐II fluorescence and photoacoustic imaging, guiding highly effective photothermal ablation of tumors. This work provides a strategic approach to developing structure‐engineered COPs for advanced cancer theranostics.