Luminescent Naphthalenediimide-Tröger's Base Covalent Organic Polymers for Selective, Sensitive, and Reversible...

Roxarsone (ROX), a widely used poultry feed additive, poses significant environmental risks when it enters wastewater streams. Consequently, its reliable detection and removal from aqueous environments are of considerable importance but remain technically challenging. In this study, we report two luminescent naphthalenediimide-based Tröger's base covalent organic polymers (COPs), namely 1,4-NDI-TB and 1,3-NDI-TB, designed for the selective and reversible sensing of ROX in aqueous media via a fluorescence "turn-off" mechanism. Notably, this work represents the first example of naphthalenediimide-based Tröger's base COPs for ROX sensing, combining high selectivity, reversibility, and effective operation in real aqueous systems. Fluorescence titration studies reveal that both COPs exhibit high selectivity toward ROX, even in the presence of competing analytes. Notably, both COPs exhibit fluorescence-quenching efficiencies exceeding 61% upon interaction with ROX. The Stern-Volmer quenching constants were determined to be 1.28 × 10⁴ M^-1 for 1,4-NDI-TB and 1.54 × 10⁴ M^-1 for 1,3-NDI-TB, indicating strong sensing performance. Furthermore, successful ROX detection in phosphate-buffered saline and untreated pond water highlights the robustness of these COPs in complex environmental matrices. Overall, these results underscore the potential of Tröger's base COPs as efficient fluorescent sensors for the selective and reversible detection of ROX in aqueous environments.