3,4-Dihydroxyhydrocinnamic acid-engineered flower-like MOF@UCNPs as robust peroxidase mimics for triple-mode H2S detection: application in pork and egg freshness monitoring

Multi-modal sensing platforms have gained significant attention due to enhanced accuracy and self-calibration capabilities, particularly within complex matrices. Targeting the demand for the real-time detection of the food spoilage marker hydrogen sulfide (H 2 S), we introduce a triple-mode sensing platform engineered via 3,4-dihydroxyhydrocinnamic-acid-directed interfacial assembly of flower-like MOF@UCNPs heterostructures that synergize intense up-conversion luminescence with potent peroxidase-mimetic activity. Sulfide selectively coordinates with the Cu 2+ nodes embedded in the MOF, concurrently (i) shutting down nanozyme catalysis, (ii) restoring up-conversion emission, and (iii) attenuating UV–vis absorbance; complementary RGB alterations captured by a smartphone furnish the third read-out. The assay delivers limits of detection of 0.06 μM (fluorescence), 0.22 μM (absorbance) and 0.90 μM (RGB imaging) with excellent linearity, and achieves satisfactory recoveries in complex food matrices. By tracking H 2 S released from meat and eggs stored at different temperatures, real-time freshness assessment is realized on a smartphone. This work not only provides a robust food freshness monitoring tool but also offers a versatile blueprint for rational design of multifunctional nanomaterials toward point-of-need analyte detection. Graphical