Structural Diversity and Fluorescent Sensing for Antibiotics and Nitrobenzene of Cd-Based Sensors With Three Tricarboxylate Isomers

Three novel Cd (II) coordination polymers (Cd-CPs) (1–3), with the formula of [Cd(2-DBB)(1,4-bibz)(OH)]·H₂O(1), [Cd₃(3-DBB)(1,4-bibz)₂]·2H₂O(2), and [Cd(4-HDBB)(1,4-bibz)_0.5](3) based on three soft organic isomers: n-(3,5-dicarboxylato benzyloxy) benzoic acid (n = 2, 3, or 4-H₃DBB), and one linear N-donor ligand 1,4-bis(1-imidazoly) benzene (1,4-bibz) have been synthesized hydrothermally and characterized by X-ray single crystal diffraction, elemental analyses, thermogravimetric, UV, IR, and PXRD technologies. The significant structural differences are both coordination polymers 1 and 3 featuring 2D networks, but 2 with 3D framework due to the change of H₃DBB isomers. Despite structural differences, the series of Cd-CPs exhibits similar fluorescence sensing properties for nitrobenzene (NB) with low detection limits of 1.05 μM (1), 44.3 nM (2), and 59.1 nM (3), respectively. However, these Cd-CPs have been discovered to detect different antibiotics, respectively: 1 had a quenching effect on ornidazole (ONZ) but 2 and 3 on chloramphenicol (CHI). The results of the theoretical calculation verified the fluorescence detection mechanism by these Cd-CPs. Therefore, these Cd-CPs might be potential luminescent sensing materials for antibiotics and NB in the future.