Clusterization‐Triggered Emission from Cellulose‐Based Luminophores in Dilute Aqueous Solution through Imine Formation

ABSTRACT Nonconventional luminescence from non‐π‐conjugated polymers has attracted increasing attention as an alternative photophysical paradigm based on clusterization‐triggered emission (CTE). However, most systems emit only in concentrated solutions or the solid state, and sustainable platforms capable of emission in dilute aqueous environments remain scarce. Herein, we report a cellulose‐based, water‐processable platform of clusteroluminogens via Schiff‐base coupling of dialdehyde carboxymethyl cellulose (DACMC) with amino compounds, affording imine‐functionalized DACMCs (IDCs). The IDCs exhibited clear fluorescence in dilute aqueous solution as low as 0.02 wt%. The photoluminescence properties depended on amine structure, and a maximum photoluminescence quantum yield of 4.2 ± 0.1% was obtained. Systematic variation of imine content and functionality revealed that C═N linkages play a decisive role in promoting CTE. Spectroscopic and computational analyses indicate that O/N‐rich hydrogen‐bonded microenvironments generate locally confined heteroatom clusters, where through‐space interactions stabilize emissive states while restricting intramolecular motion. Furthermore, the IDCs enable class‐selective detection of tetracycline antibiotics in water via an inner‐filter‐effect‐mediated quenching mechanism with sub‐micromolar limits of detection. This work establishes a sustainable polysaccharide‐based platform for dilute‐solution CTE luminophores and provides a general strategy for controlling cluster density and heteroatom environments in aqueous photofunctional materials.