Versatile Fluorescent Cellulose‐Based Materials via Hydroxyl–Yne Click Chemistry

ABSTRACT Cellulose‐based fluorescent materials are attractive for sustainable applications owing to their biocompatibility and biodegradability; however, their practical utility is often limited by aggregation‐caused quenching (ACQ) and insufficient functional diversity. Here, we report a versatile strategy to construct aggregation‐induced emission (AIE)‐active cellulose materials via an organobase‐catalyzed hydroxyl–yne click reaction, enabling the efficient incorporation of tetraphenylethene (TPE) units into the cellulose backbone. The resulting EC‐TPEs exhibit high optical transparency (>95%), full UV‐shielding capability, and intense fluorescence, allowing simultaneous UV protection and real‐time optical indication. Notably, the fluorescence properties can be precisely tuned by controlling the grafting ratio, enabling multicolor emission and the fabrication of high‐resolution fluorescent quick response (QR) codes. Furthermore, secondary grafting of AIE‐active MTPAP unit affords an acid‐responsive system of EC–TPE–MTPAP with dynamic fluorescence color switching, facilitating advanced multicolor encryption and high‐density information storage. Importantly, the dynamic enol ether linkages formed via the hydroxyl‐yne click reaction enable an efficient amine‐exchange defunctionalization process, restoring cellulose hydroxyl groups without loss of reactivity. This work establishes a reversible and modular platform for engineering multifunctional fluorescent cellulose materials, offering new opportunities for sustainable optical materials and information technologies.