Two 3D Zn(II)/Ni(II) coordination polymers with distinct cluster nodes for selective fluorescence sensing in aqueous media

Two three-dimensional luminescent coordination polymers, CP1 (C48H36N10O15Zn3) and CP2 (C15H10N4Ni2O7), were synthesized via a solvothermal strategy and characterized by single-crystal X-ray diffraction. CP1 features a three-dimensional Zn(II)-based framework, whereas CP2 contains tetranuclear Ni(II) secondary building units. Both polymers exhibit good thermal stability and excellent structural integrity in aqueous media. Fluorescence sensing experiments demonstrate that CP1 selectively detects Fe³⁺ ions, with a Stern–Volmer quenching constant (Ksv) of 8.74 × 104 M−1 and a detection limit (LOD) of 3.20 μM. In contrast, CP2 shows high selectivity toward CrO₄²⁻ anions, with a Ksv of 1.27 × 105 M−1 and an LOD of 1.23 μM. Mechanistic investigations suggest that fluorescence quenching is primarily associated with competitive absorption of excitation energy through the inner filter effect (IFE), while differences in metal centers and framework architectures may contribute to analyte selectivity. These findings highlight the potential of water-stable coordination polymers for selective fluorescence detection of ionic pollutants in aqueous environments.