A Multifunctional Eu ³⁺ @Cd‐Metal–Organic Framework Probe for Ratiometric and Smartphone‐Assisted Detection of Antibiotics and Fe ³⁺

The overuse of antibiotics and metal ions, despite their benefits in medical and industrial applications, poses a significant threat to environmental safety and human health. In this work, a near‐white‐light‐emission metal–organic framework (MOF), Eu 3+ @Cd‐MOF, was designed as a fluorescent probe for the colorimetric and fluorescent detection of these pollutants. The probe exhibits highly selective and sensitive responses to ciprofloxacin (CIP), tetracycline (TET), and Fe 3+ via distinct fluorescence changes: the addition of TET or Fe 3+ quenches both the 475 and 618 nm emission peaks, whereas CIP enhances the intensity at 475 nm while leaving the 618 nm peak nearly unchanged. Based on these spectral responses, the sensor achieves high sensitivity with detection limits of 0.034 mM (CIP), 0.13 mM (TET), and 0.369 mM (Fe 3+ ), together with good recyclability. Furthermore, a smartphone‐assisted sensing platform using Eu 3+ @Cd‐MOF and Eu 3+ @Cd‐MOF/PSF MMMs (PSF = Polysulfone, MMMs = mixed‐matrix membranes) were developed, enabling rapid and visual pollutant detection. This work provides a reliable, portable, and sensitive sensing platform for environmental monitoring, contributing to ecosystem protection and public health.