A Schiff-base covalent-organic polymer incorporating phosphate ester and benzimidazole units for turn-on fluorescent detection of Zr ⁴⁺

The potential persistence of zirconium ions (Zr 4+ ) in environmental and biological systems poses significant risks, underscoring the critical need for rapid, sensitive, and highly selective detection methods. In this study, a Schiff base-type organic fluorescent polymer designated as TFMP-APBIA, was successfully synthesized via a solvothermal method using tris(4-formyl-2-methoxyphenyl) phosphate (TFMP) and 2-(4-aminophenyl)-1H-benzimidazol-5-amine (APBIA) as building blocks. Experimental results demonstrate that TFMP-APBIA functions as a “turn-on” fluorescent probe capable of highly selective recognition of Zr 4+ , achieving a limit of detection (LOD) as low as 4.7 × 10 -6 M. The polymer exhibits robust solvent adaptability and exceptional acid-base stability, maintaining consistent fluorescence performance across a pH range of 4 - 10. Mechanistic investigations reveal that the fluorescence response to Zr 4+ originates from a synergistic coordination effect involving the phosphate ester and the imine units. Leveraging its high sensitivity, selectivity, and superior anti-interference capabilities, test strips based on TFMP-APBIA were fabricated to enable the visual detection of Zr 4+ in real water samples. Consequently, TFMP-APBIA demonstrates significant potential for the analytical detection of Zr 4+ in environmental matrices, offering new insights for the design of advanced fluorescent sensing materials.