Crystal Transformation Synthesis of a Three-Dimensional Dual-Fold Building Block Derived from Metal–Organic Framework for Tetracycline Detection

Metal–organic framework (MOF)-based sensors, which have garnered considerable focus for their potential to enhance environmental monitoring and improve water quality by accurately and consistently identifying antibiotic compounds in water, have gained considerable interest. With the help of pH value, an unusual instance of single-crystal-to-single-crystal (SCSC) transition from the three-dimensional (3D) Zn-framework {[Zn2(mbix)2(2,5-bda)2]·H2O}n (1) to the 3D 2-fold Zn-framework {[Zn4(mbix)4(2,5-bda)4]·H2O}n (2) has been observed under mild conditions. This transformation necessitates the replication of structure 1 while simultaneously modifying the angle between the planes of the imidazole and benzene rings. It is noteworthy that the detection capabilities of 2 for tetracyclines (TC) surpass those of other antibiotic analytes in water. Furthermore, the sensing results are in close consistency with the S–V model when TC concentrations fall within the range of 0–0.08 mM. Additionally, the limit of detection (LOD) of the sensor toward TC is estimated to be 0.59 nM. The stronger quenching impact seen for TC can be linked to a more significant overlap in the energy transfer process. The aforementioned proposition presents a viable strategy for the systematic fabrication of economically viable luminescent sensors, thereby enabling efficient and cost-effective modifications of properties.