Single-entity dual-emissive MOF platform for reliable ratiometric point-of-care detection of amoxicillin residues

In fluorescence-based sensing, self-referencing ratiometric analysis offers a significant advantage over external referencing by integrating both the probe and reference signals within a single material, rather than relying on two separate components. This intrinsic approach eliminates the need for additional reference dyes or materials, which can introduce inconsistencies due to variations in concentration, uneven dispersion, or environmental instability. Self-referencing materials provide a built-in correction mechanism, enhancing detection accuracy, reliability, and reproducibility while minimizing background interference. Despite their advantages, the design and synthesis of dual-emitting metal-organic frameworks (MOFs) with self-referencing capabilities remain rare and challenging. In this study, we introduce a novel Eu-based MOF with intrinsic dual-state, dual-emission properties, exhibiting distinct blue and red fluorescence in both liquid and solid states. The blue emission arises from the coordination-induced emission of the free, non-emissive ligand within the MOF structure. Interestingly, the red emission is selectively quenched by amoxicillin (AMX), while the blue fluorescence remains unaffected. This unique dual-emission feature enables a ratiometric sensing platform without requiring an external reference, ensuring greater stability, accuracy, and ease of use. With a linear detection range of 8.0-218 μM and a limit of detection of 0.354 μM, this Eu-MOF offers a robust and selective AMX sensing strategy. Additionally, a smartphone-assisted visual detection method using RGB analysis via the Color Grab App was developed, enabling portable and on-site quantification. This self-referencing Eu-MOF is inherently stable, recyclable, providing consistent signals and making it highly effective for pharmaceutical applications.