High-Sensitivity Fluorescence Detection of Malachite Green in Aquaculture Using a Zirconium-Based Metal-Organic Framework PCN-128

• • PCN-128 fluorescent probe achieves an ultra-low LOD of 2.73 nmol·L−1 for malachite green, enabling trace detection at parts-per-billion levels, critical for regulatory compliance where MG is banned. • • The method exhibits a broad linear range of 0.0–7.0 μmol·L−1, allowing quantification across a wide concentration span without dilution, streamlining high-throughput screening. • • Exceptional selectivity is demonstrated against 13 veterinary drugs, and anti-interference is validated against 16 anions, 16 cations, and 12 additional veterinary drugs, ensuring reliable detection in complex biological and environmental matrices. • • Spike-and-recovery tests in real samples (aquaculture water and fish) show recoveries of 89.80%–113.7% with RSD ≤ 2.59%, confirming accuracy and precision suitable for routine food safety monitoring.