Multifunctional Benzene‐Cored Covalent Organic Polymer via IEDDA Click Chemistry for Iodine Capture and pH ‐Responsive Drug Delivery

Abstract

ABSTRACT Covalent organic polymers (COPs) with tunable functionality hold strong potential for pollutant capture and drug delivery. We report the synthesis of a benzene‐cored COP (BeTz‐COP) via a metal‐ and catalyst‐free inverse electron‐demand Diels–Alder (IEDDA) reaction between a tetra‐norbornene‐functionalized benzene monomer and a bifunctional tetrazine linker. This modular approach enables access to multifunctional materials under mild conditions. BeTz‐COP was characterized using FTIR, SEM, EDX, TEM, and TGA, confirming its robustness. UV–Vis diffuse reflectance spectroscopy revealed a band gap of 2.01 eV for BeTz‐COP, compared to 1.66 eV for the porphyrin‐based PoTz‐COP, as we previously reported, highlighting the impact of core structure on optoelectronic properties. Both polymers are semiconducting in optoelectronic behavior and hold promise for photocatalysis, biosensing, and light‐triggered drug delivery. In cyclohexane, BeTz‐COP exhibited an iodine uptake of 547 mg·g −1 , surpassing PoTz‐COP (462 mg·g −1 ), underscoring the aromatic core's effect on adsorption. At pH 8.50, drug loading efficiencies were 23.0% for BeTz‐COP and 31.0% for PoTz‐COP. Both materials showed pH‐responsive doxorubicin release, with faster release under acidic conditions (pH 5.50, mimicking tumor pH) and prolonged release at physiological pH (7.40), supporting targeted drug delivery. IEDDA chemistry offers a versatile platform for designing adaptive COPs for environmental and biomedical applications.