Three new Zn (II)-based coordination polymers: Optical properties and dye degradation against RhB

Abstract

Three newly developed coordination polymers (CPs), denoted as [Zn2(HL)(ptp)2]n(1), [Zn(HL)(bpz)·0.25H2O]n(2) and [Zn(HL)(bic)·H2O]n(3), have been synthesized using hydrothermal methods. These CPs are composed of zinc ions and specific ligands with 3-(4-carboxyphenoxy)-5-methylbenzoic acid (H3L); 3,5-bis(4-pyridyl)-1,2,4-triazolyl (ptp); 3,3ʹ,5,5ʹ-tetramethyl-4,4ʹ-bipyrazole (bpz) and 3,6-bis(imidazol-1-yl)-9H-carbazole (bic) which provide oxygen and nitrogen donor sites. The molecular structures of the CPs were determined through single X-ray diffraction analysis, revealing a tetrahedral geometry. The CPs 1–3 have distorted tetrahedral geometry. The layered structural progression, starting from the tetrahedral complex and moving towards 1D, 2D, and potentially 3D networks, showcases the intricacies and hierarchical nature of CP 1–3’s molecular architecture. An interesting property of these CPs is their semiconducting nature. They exhibit the ability to serve as photocatalysts, especially against organic pollutants such as Acid chrome blue (ACB), Methyl blue (MB), Methyl orange (MO), and Rhodamine B (RhB). Among the CPs, CP 1 demonstrates superior photocatalytic activity against RhB (RhB) at a concentration of 25 mg/L. This suggests that CP 1, when used in a quantity of 25 mg, exhibits enhanced efficiency in degrading RhB through photocatalysis. The optimal conditions, where 25 mg/L RhB and 25 mg of CP 1 are employed, result in the degradation of an impressive 97.51 % of RhB.