σ–p Hyperconjugation–Enabled Covalent Organic Frameworks for Programmable Cascaded Optical Modulation

ABSTRACT σ–p hyperconjugation is identified as an effective molecular lever for regulating the excited‐state behavior and donor characteristics of covalent organic frameworks (COFs). Activation of σ–p hyperconjugation amplifies the fluorescence quantum yield of COFs by up to 167‐fold, accompanied by a pronounced redistribution of excited‐state charge density. This atomic‐level electronic regulation enables programmable control over both the direction and magnitude of interfacial charge transfer in COF‐OMe/Eu@UiO‐66‐(COOH) 2 heterojunctions, giving rise to cascaded excitation–emission coupling and excitation‐dependent multicolor outputs. Perturbation of the hyperconjugation‐enhanced interface by hormone binding modulates the interfacial charge‐transfer landscape, resulting in distinct optical fingerprints that reflect subtle molecular stimuli. When incorporated into electrospun polyacrylonitrile membranes, these programmable optical responses are preserved in a flexible, antibacterial, and machine‐learning‐readable format, enabling rapid visual readout, quantitative concentration discrimination, and efficient solid‐phase extraction. Conceptually inspired by the multilayered optical modulation of chameleon skin, this work establishes σ–p hyperconjugation as a general design principle for constructing electronically adaptive COF–MOF heterostructures capable of transducing molecular perturbations into tunable optical signals.