<p>Real-time sensing applications demand dual-emitting materials with built-in self-referencing capabilities to minimize background interference and enhance detection accuracy. Despite their significant potential to improve sensor reliability, sensitivity, and longevity, the fabrication of metal-organic frameworks (Eu-MOFs) with both dual-emission characteristics and dual-state behavior remains rare and technically challenging. The intricate design and precise control required for such structures make their successful synthesis an ongoing challenge in materials science. In this work, we report the synthesis of a new Eu-based MOF that displays dual fluorescence, emitting both blue and red light in liquid and solid states. The blue emission arises from coordination-induced ligand luminescence upon integration into the MOF framework. Notably, the red emission is selectively quenched in the presence of diclofenac (DCF), while the blue emission remains stable. This dual-emission property enables the construction of a ratiometric sensing platform, where the unaffected blue fluorescence acts as an internal reference and the quenched red fluorescence provides the detection signal for DCF. The developed method achieves a Linear detection range of 0–231 µM with a detection Limit of 0.2 µM. In addition, a smartphone-based visual sensing strategy was applied through RGB analysis, enabling convenient and on-site quantification. Since the Eu-MOF functions as an intrinsic sensor without the need for encapsulation or surface modification, it demonstrates excellent stability, recyclability, and selectivity, highlighting its strong potential for practical analytical applications.</p> Graphical Abstract <p></p>