MB-encapsulated MOF-based composites as self-calibrating sensors for selective detection of tetracycline and nitroanilines

It is well known that the introduction of dye molecules into metal-organic frameworks (MOFs) can produce self-calibrating fluorescent sensors. In this work, we successfully constructed two dual-emission composites, MB@ZnMOF1 and MB@ZnMOF2. These composites are based on ZnMOFs synthesized using the organic ligands 5-((4-carboxyphenyl)formylamino)thiophene-2-carboxylicacid (L₁) and 2,5-bis-(3,4-dicarboxyphenyl)thiopheneamide (L₂), respectively, with the luminescent dye methylene blue (MB) encapsulated within their pores. Inspired by the dual-emission properties of these MB@ZnMOFs, we investigated their potential as fluorescent sensors for antibiotic compounds and aromatic amines. The results demonstrate that MB@ZnMOFs function effectively as multi-target sensors for selective detection of tetracycline and nitroanilines, with good anti-interference capability and cyclic stability. In addition, the dual-emission peaks of the MB@ZnMOFs both exhibit pronounced fluorescence changes upon interaction with analytes, enabling them to serve as self-calibrated fluorescent probes to detect tetracycline and nitroanilines. The possible quenching mechanism can be attributed to a competitive absorption between the MB@ZnMOFs and the analytes.