Photoinduced Electron Transfer-Driven Imine-Linked Nanoscale Covalent Organic Polymer as Turn-On Fluorescence Sensor for Uranium Ion Detection

Uranium is a critical element for nuclear energy, but its chemical toxicity and radioactivity pose significant threats to ecosystems and public health. Here, we present a fluorescent sensor based on an imine-linked nanoscale covalent organic polymer (TFPA-TAPB COP) for UO22+ detection. This COP was synthesized by a one-step Schiff-base condensation between tris(4-formylphenyl)amine (TFPA) and 1,3,5-tris(4-aminophenyl)benzene (TAPB). Mechanistic investigations reveal that the formation of N–U coordination bonds restricts the photoinduced electron transfer (PET) process, thereby suppressing nonradiative transitions and leading to fluorescence enhancement. The sensor demonstrates not only excellent sensitivity and selectivity, but also a linear response over the concentration range of 0.10–2.00 μM, with a detection limit of 61.10 nM. Spiking experiments on environmental samples yielded recovery rates ranging from 92.00% to 106.20%. The method has been successfully applied to real water and urine samples, validating its practical applicability to environmental monitoring of UO22+.