Dual-Responsive Flower-Like Luminescent Zinc(II) MOF for Visual Detection of Nitroaromatics and Antibiotics in Aqueous Medium: Experimental and Theoretical Perspectives

High Resolution Image Download MS PowerPoint Slide A new zinc(II) based metal organic framework [Zn 3 (H 2 L 2 ) 6 ] (ZnB-MOF) was synthesized through self-assembly using ligand H 2 L 2 ((E)-N′-(3-ethoxy-2-hydroxybenzylidene)thiophene-2-carbohydrazide). Single-crystal X-ray diffraction analysis shows that ZnB-MOF forms a stable three-dimensional framework. Density Functional Theory (DFT) calculations were carried out to optimize the geometry of the material and examine the HOMO–LUMO characteristics, providing insights into its electronic properties. Notably, ZnB-MOF displays strong fluorescence in aqueous solution, making it a promising luminescent probe for highly sensitive and selective detection of nitroaromatic contaminants and antibiotics. The framework exhibited remarkable fluorescence quenching efficiency of 97.57% and 98.39% toward nitroaromatics 2,4-dinitrophenol (2,4-DNP) and 2-nitroaniline (2-NA), respectively, along with 98.11% and 94.9% for antibiotics tetracycline (TC) and oxytetracycline (OTC). Mechanistic investigation indicated that the observed fluorescence quenching was mainly driven by photoinduced electron transfer (PET) and absorption-competitive quenching (ACQ) mechanisms. For practical implementation, ZnB-MOF was incorporated on a filter paper to form a portable fluorescent sensing strip. These strips provide an easy, cost-effective, and quick visual tool for detecting 2,4-DNP, 2-NA, TC, and OTC with their fluorescence changes visible to the naked eye. This approach highlights the potential of ZnB-MOF for real-time environmental and pharmaceutical monitoring in field conditions.