Fabrication of a water-stable luminescent MOF with an open Lewis basic triazolyl group for the high-performance sensing of acetone and Fe³⁺ ions

A 3D chemically stable MOF of {[Cd_1.5(DBPT)(DiPyDz)(H₂O)]·3.5H₂O}_n (1) was successfully synthesized by a hydrothermal process, with the help of multifunctional ligand of H₃DBPT (3-(3,5-dicarboxylphenyl)-5-(4-carboxylphenyl)-1-H-1,2,4-triazole) and bridging ligand of 1,2-di(pyridine-4-yl)diazene (DiPyDz). Characterizations of PXRD, FT-IR, TG and PL analysis for compound 1 were implemented. The overall structure maintains thermally stable up to 354 °C and keeps structural stability in common solvents after 48 h immersion. Most strikingly, it could maintain the crystallinity in water even for 10 days. It exhibits strong emission peak centered at 412 nm upon excitation at 280 nm, which could be attributed to the intra-ligand charge transfer of the H₃DBPT ligand. It has proved itself an efficient sensor not only for acetone at low concentration but also for Fe³⁺ ion. The detection limit is estimated to be 0.0013% (v/v%) for the acetone, and 78 ppb for the Fe³⁺ ion, respectively. The K_SV value for sensing Fe³⁺ ion is calculated to be 4.78 × 10⁵ M⁻¹, which is the third top one among the reported excellent MOFs-based sensors. The sensing performance is not affected even in the existence of interference metal ions, which reflects the high application potentials for the effective detection of Fe³⁺ in an aqueous system.