Synthesis and characterization of mixed ligands based Co(II)-based coordination polymers and study their photochemically antibiotic degradation

Abstract

Two Co(II)-based coordination polymers （CPs）, denoted as [Co4(NPDA)4(bmb)2·3H2O]n (1) and [Co(CHDA)(bmb)]n (2) (bmb = 4, 4́-bis(2-methylimidazol-3-ium-1-yl) biphenyl; H2NPDA = 1,4-naphthalenedicarboxylic acid; H2CHDA = 1,4-cyclohexanedicarboxylic acid), were obtained from mixtures of Co(NO3)2·6H2O and H2NPDA and bmb for 1 or H2CHDA and bmb for 2 with good yields (67 % and 53 %). Single crystal XRD shows a quadruply acetate-bridged Co(II)···Co(II) center for 1 with distorted triangular bipyramid surrounding of Co atom, while 2 shows a cis-configured octahedral N2O4 coordination for Co. Thermal gravimetric analysis confirms the water content of 1 and shows remarkable thermal stabilities, with a decomposition for 1 at around 400 °C and 450 °C for 2. 1 and 2 were used as catalysts for the photochemical degradation of the antibiotics secnidazole (SIZ), nitrofurazone (NFZ), sulfasalazine (SLA), and furazolidone (FZD). Using 1 at a dosage of 10 mg/L allowed a degradation efficiency of 92.3 % for 30 ppm NFZ at 6.5 pH. A proposed photodegradation mechanism was investigated through radical trapping experiments.