A nonporous Cd(II) coordination polymer based on a new triangle imidazole‒carboxylic ligand for iodine adsorption and tetracyclic antibiotic detection

Abstract

A new Cd(II) coordination polymer (CP) based on (3,3′-(4-(4-(1H-imidazol-1-yl)phenyl)pyridine-2,6-diyl)dibenzoic acid (H₂IPPDA), namely, [Cd(IPPDA)(H₂O)]_n (Cd-IPPDA), was constructed. It exhibits a two-dimensional coordination network with a (4·8²) topology, and the 2D networks are packed into a 3D supramolecular framework via hydrogen bonds. Interestingly, Cd-IPPDA is capable of absorbing iodine molecules with a capacity of 3.4 g/g, although it has no significant pores in the framework. A mechanistic study revealed that the strong interactions between the iodine molecules and the framework cause the transformation from crystalline nonporous to porous amorphous structures. The resulting porous amorphous network, namely, a-Cd-IPPDA, still showed good iodine adsorption performance. It’s capacity was 3.0 g/g but adsorption kinetics significant increased, and could be reused for at least five cycles without a significant capacity decrease. In addition, the luminescence intensity of Cd-IPPDA was quenched by tetracyclines (TCs) in water; thus, this material can be used as a sensor for detecting TCs. The detection limits for OXY, CTE, and GEN are 0.51, 0.93, and 0.42 μmol/L, respectively. Moreover, the detection selectively is also good. The internal filtering effect and fluorescence resonance effect contribute to fluorescence quenching.