A Schiff Base-Functionalized Europium Metal-Organic Framework for Turn-off Fluorescence Sensing of Cu2.

Developing a low-cost, highly sensitive, and accurate fluorescence-based approach for Cu2+ detection is crucial for reducing heavy metal pollution in industrial effluent. Here, we report a newly synthesized Schiff base europium metal-organic framework (Eu-MOF) and demonstrate its use for turn-off fluorescent detection of Cu2+. A Schiff base ligand derived from 2-aminoterephthalic acid and 2-hydroxynicotinaldehyde was coordinated with Eu3+ to construct the framework, enabling a simple and rapid sample pretreatment procedure. The material exhibited pH-dependent fluorescence behavior. With the concentration range of 2.5 to 500 mg L-1, a linear response to Cu2+ was observed. The limit of quantification (LOQ) was 2.5 mg L-1, while the limit of detection (LOD) was 0.83 mg L-1. The method was effectively performed on vinegar, tea, fruit juice, and water samples, yielding spike recoveries of 84.5%-100.9% and relative standard deviations (RSDs) of 1.7%-4.8%. This method can be used to determine Cu2+ in various matrices.