Ligand-Substitution Engineering Enhances Fluorescence Sensing of Antibiotics in Cadmium-Organic Frameworks

The environmental accumulation of nitrofuran antibiotics, exemplified by nitrofurazone (NZF), poses significant risks to ecosystems and public health, necessitating sensitive and rapid detection methods. Herein, we report a cadmium-based metal-organic framework (Cd-MOF) featuring a 2D → 3D interpenetrated structure and a noncoordinating N-containing ligand within its pores. This MOF acts as a selective fluorescence-quenching sensor for nitrofurazone (NZF) with a detection limit of 1.19 μM among other nitrofuran derivatives. By exploiting a ligand-substitution strategy, we exchanged the free ligand with the fluorescent aniline dye molecule to construct a dual-emission composite, DSM@Cd-MOF. This postsynthetic engineering fundamentally transforms the sensing response from quenching to a distinct ratiometric fluorescence enhancement, achieving a significantly lower detection limit (0.30 μM) and enabling clear visual discrimination. Both sensors demonstrate high reliability in real water samples, with recovery rates of 97.1-102.1%. This study establishes ligand-substitution as a powerful and generalizable strategy for tailoring the functionality of MOF-based sensors, providing an effective platform for monitoring antibiotic pollutants in environmental and biomedical settings.