Pyridinyl conjugate of uio-66-nh₂ as chemosensor for the sequential detection of iron and pyrophosphate ion in aqueous media

A new chemosensor UiO-66-N-Py (Py = 2-methinepyridine, N = imine nitrogen) based on isoreticular UiO-66 (University of Oslo) Metal–Organic Framework (MOF) containing 2-methinepyridine functionalized organic linker was solvothermally synthesized and characterized. This UiO-66-N-Py was very selective and sensitive for detecting the Fe³⁺ ion and sequential detection of the pyrophosphate (PPi) anion. The limits of detection for the Fe³⁺ ion and PPi were calculated to be 10 ppb (0.19 µM) and 50 ppb (0.3 µM), respectively. The quenching constant K_sv for Fe³⁺ and the binding constant for PPi were 1.4 × 10⁵ M⁻¹ and 1.7 × 10⁵ M⁻¹, respectively. The functionalization of UiO-66-NH₂ with 2-methinepyridine enhanced its fluorescence emission properties and introduced more binding sites for the analytes. We additionally studied the interaction of the sensor and the analytes with Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). This chemosensor also demonstrated a regenerative emission property without loss in the detection ability for six consecutive cycles.