Fabrication of Co(II)-based coordination polymer for photocatalytic degradation: Selective removal of cationic methyl violet dye

In this study, a new coordination polymer (CP) was designed and synthesized to evaluate the photocatalytic properties for water remediation. The Co(II)-based CP {[Co(HL)(bid)(H₂O)]·2H₂O}_n (1) was hydrothermally synthesized using the ligand 5-(4′-carboxyphenoxy)isophthalic acid (H₃L) and 1,4-bis(1-imidazolyl)-2,5-dimethylbenzene (bid). The coordination polymer (1) has been characterized by various spectral techniques, thermogravimetric (TGA), and single crystal X-ray technique. X-ray data revealed that (1) exhibits 2D framework having an octahedral coordination geometry around the Co(II) ions, having μ_1:η¹-η¹ mode with chromophore CoO4N. FT-IR analysis confirmed the asymmetric monodentate binding modes of the carboxylate ligand. The CP 1 has demonstrated optical semiconducting properties, rendering them promising candidates for photocatalytic applications. The catalyst (1) has been effectively utilized in the breakdown of several organic dyes, such as methylene blue (MB), methyl orange (MO), methyl violet (MV), and rhodamine B (RhB). The results showed that at pH 4, with a dosage of 30 mg of catalyst (1), 92.08 % of MV was degraded at a concentration of 20 ppm. Additionally, the mechanistic pathway for light-driven MV decomposition was investigated through experimental approaches, specifically radical trapping experiments.