Triple-Interpenetrated Lanthanide-Organic Framework as Dual Wave Bands Self-Calibrated pH Luminescent Probe

Abstract

pH value is a key parameter in reflecting the health status, reaction process, and water quality. The construction of highly sensitive pH luminescent ratiometric is important but challenging. Herein we designed and synthesized a unique triple-interpenetrated luminescent lanthanide-organic framework {[Eu(PPTA)_0.5(NO₃)(DMF)₂]·H₂O} _n(V104) based on an amphoteric ligand 4,4',4'',4'''-(1,4-phenylenebis(pyridine-4,2,6-triyl))tetrabenzoic acid (H₄PPTA). Compound V104 possesses high solvent and acid/alkaline stabilities. Luminescent investigations reveal that V104 exhibits dual emission peaks at 390 and 480 nm, and these two peaks can separately detect OH^- and H⁺ among various anions and cations. Importantly, V104 can serve as a self-calibrated pH ratiometric to quantitatively detect pH value, and the sensitivity can reach 403.2% per pH for OH^-, and 129.5% per pH for H⁺. Furthermore, by encapsulating magnetic γ-Fe₂O₃ nanoparticles in V104, the pH sensor can be readily separated from the analyte by external magnet and recycled at least four times, suggesting as-synthesized γ-Fe₂O₃@V104 has potential for monitoring pH fluctuations in water. To our knowledge, this is the first self-calibrated ratiometric pH-sensor based on two responsive wave bands which can separately detect OH^- and H⁺.