Single‐Amino Group Counted Rotation‐Restriction in Eu‐BTB‐NH ₂ MOF for Accurate Detection of Methcathinone

MOF probe exhibits a pronounced fluorescence emission change from red to emerald green under UV excitation, together with a fast response (<1 s) and a desirable limit of detection (LOD) of 21 ng/mL, highlighting the sensing material's potential for methcathinone early-warning. Furthermore, a portable sensing chip and a custom-built Drugs Analyst device are introduced, which enabled rapid, on-site methcathinone detection in various complex matrices such as urine, sewage, alcohol, etc., as well as a seized item, thereby demonstrating strong practical applicability. This work provides a mechanistically guided sensing strategy for desirable illicit drug detection in complex real-world environments and offers valuable insights into the design of rotation-restricted luminescent MOFs for optical sensing.