Two new d10-based transition metal coordination polymers used for antibiotic degradation

Abstract

In this study, we synthesized two new coordination polymers (CPs), [Cd₂(bbpy)(L)₂(DMF)₂]_n (1) and [Zn₂(bbpy)(L)₂(DMF)₂]_n (2) ((bbpy = 3,5-bis(benzoimidazo-2-ly)pyridine and H₂L = 4,4′-((1,2-phenylenebis(methylene) bis(oxy))dibenzoic acid)), using a solvothermal method. The optical band gaps of CP 1 and 2, determined using UV–visible spectroscopy, were 2.3 eV and 2.1 eV, respectively. Both CPs demonstrated strong photocatalytic activity for the degradation of various antibiotic pollutants under UV light, with CP 2 showing superior efficiency, particularly for metronidazole (MDZ), achieving 90.89 % degradation. The optimal photocatalytic conditions for CP 2 were a catalyst dosage of 5 mg/L, an MDZ concentration of 40 ppm, and a neutral pH. The stability and reusability of the photocatalyst were confirmed through multiple cycles of use. Radical trapping experiments identified superoxide radicals (O₂̇⁻) as the primary active species in the photocatalytic process. The photocatalytic efficiency of CP 2 was further tested in different water sources, with degradation rates of 87.99 % in tap water, 80.49 % in river water, and 92.13 % in deionized water. The presence of inorganic anions such as Cl⁻, NO₃⁻, and CO₃²⁻ was also studied, with CO₃²⁻ having the most significant inhibitory effect on the degradation efficiency. These results suggest that CP 2 is a promising candidate for practical wastewater treatment applications.