New Cd(II)-based 3,5-bis(3'-carboxy-phenoxyl)-1,2,4-triazole appended coordination polymers with varied imine Co-ligands: Structural diversity and multi-target detection.

The increasing complexity of pollutants in aquatic environments poses significant challenges to traditional fluorescence sensing strategies based on the "one-sensor-one-target" principle, which struggle to meet demands for rapid and efficient detection. In this study, three novel Cd(II)-based coordination polymers with compositions [Cd(L)(bib)] (1), [Cd(L)(phen)] (2), and [Cd(L)(2,2'-bipy)] (3) were successfully synthesized and developed as fluorescent sensing materials. These were constructed using 3,5-bis(3'-carboxy-phenoxy)-1,2,4-triazole (H2L) as the primary ligand, in conjunction with auxiliary ligands including 1,4-bis(1-imidazolyl)benzene (bib), 1,10-phenanthroline (phen), and 2,2'-bipyridine (bipy). The primary ligand, with its abundant coordination sites and unique functional groups, formed a stable material framework, while the auxiliary ligands provided optimal π-conjugated systems and enhanced electron delocalization capabilities. Results demonstrated that among the three coordination polymers, 1 exhibited exceptional photoluminescence sensing performance for baicalin (BCL), Fe3+, and CrO42-, achieving detection limits of 1.32 μM, 10.6 μM, and 48.1 μM, respectively, with Stern-Volmer constants of 1.06 × 10-5, 0.13 × 10-5, 0.03 × 10-5 M-1. Integrated experimental and theoretical analyses revealed that the observed photoluminescence quenching arose from the inner filter effect, energy transfer, and non-covalent interactions between the coordination polymer and analytes. Fabricated test strips based on this material successfully identified the three pollutants with user-friendly operation and rapid response. This work provides a promising technical pathway for on-site and real-time detection of environmental contaminants.