An ultra-stable Cadmium(II) Coordination Framework Constructed From the new Bi-Functional Ligand and Application as Fluorescent Probe for Acetylacetone and Antibiotics

In the last thirty years, light-emitting metal organic frameworks (MOFs) sensors have attracted immense interest by scientists because these functional coordination materials possess good framework stability and high surface areas, and excellent stability in adsorption, separation, catalysis, etc. These MOFs-based sensors have the broad applications in the national security, surrounding protection and mankind's health. In this work, a new bi-functional ligand H3L (H3L = 4'-(1H-tetrazole-5)-biphenyl-2,3-dicarboxylic acid) simultaneously containing tetrazole and carboxylate groups can be synthesized. Further, the ultra-stable tetrazolium Cadmium (II) MOFs {[Cd2 (μ7-L) (μ3-OH) (H2O)2]·1.3H2O}n (1) has been successfully prepared under the solvo-thermal conditions. In 1, neighboring tetranuclear cadmium (II) building blocks are inter-linked through the bridging tetrazole moieties and aromatic bi-phenyl backbones forming the 3D micro-porous framework. It is interesting that 1 exhibits excellent chemical stability, the coordination framework of 1 can be kept not only in various different solvents but also the water environment with pH varying from 2 to 12 for 24 h. Powder X-ray diffraction (PXRD) patterns have been investigated demonstrating these bulky as-synthesized samples 1 are pure phases. Compared with other coordination polymers, 1 has some other advantages such that 1 possesses good water dispersibility, excellent photo-luminescence emissions and fluorescence stability, which has the potential to be utilized as the excellent chemical sensor. Fluorescent characterization reveals that 1 also can behave highly sensitive and real-time discrimination of acetylacetone (Hacac) with good reusability (high quenching efficiency Ksv for Hacac: 2.5 × 105 M−1) and extremely low detection limit values (For Hacac: 35 μM). On the other hand, 1 can behave highly sensitivity, recyclability and real-time chemical sensing for antibiotics nitrofurazone (NFZ) and nitrofurantoin (NFT) (Ksv for NFZ: 5.9 × 106 M−1 and NFT: 9.0 × 106 M−1) and extremely low detection limit values (For NFZ: 2.2 μM and NFT: 1.4 μM).