A cadmium-based coordination polymer as multifunctional fluorescent sensor for simultaneous detection of heavy metal ions and antibiotics in water

This work successfully constructed a new three-dimensional coordination polymer [Zn(HEA)(L1)]_n (1) based on o-phenylenediacetic acid (H₂HEA) and 1,1′-(2,4,6-trimethyl-1,3-phenylene) bis(methylene) bis(1H-imidazole) (L1), demonstrating exceptional thermal stability and solvent resistance. The unique two-dimensional architecture of complex 1 features a distinctive “W”-shaped topology, assembled through the interconnection of nitrogen-rich and oxygen-containing coordination chains. These 2D layers subsequently extend into a three-dimensional framework via π–π stacking interactions and interlayer hydrogen bonding, creating a stable and porous network structure. As a multifunctional fluorescent probe, complex 1 exhibits remarkable sensing capabilities towards aqueous CrO₄²⁻, Cr₂O₇²⁻, and Fe³⁺ ions, and antibiotics including Ornidazole (ODZ) and Nitrofurazone (NFZ), with detection limits below 0.058 μM. Mechanistic investigations combining UV–vis absorption spectroscopy and density functional theory (DFT) calculations revealed that the fluorescence quenching originates from competitive energy absorption for metal ions, while a synergistic effect of photoinduced electron transfer (PET) and energy absorption accounts for antibiotic detection. Practical applicability was validated through real water sample analysis, achieving recovery rates of 97.3 %–103.7 % with relative standard deviations below 4 %. This study provides a new strategy for the simultaneous detection of multiple pollutants and expands the design principles for multifunctional fluorescent probes.