Sensitive luminescent chemosensing of fluoride based on Eu-doped Zn-LMOF in aqueous media: structural and spectroscopic studies

• Published in: CrystEngComm 2023-07, Vol.25 (26), p.3766-3776
• Main Authors: Toledo-Jaldín, Helen Paola, Pinzón-Vanegas, Cristian, León-Gómez, Juan Pablo, Blanco Flores, Alien, Martínez-Otero, Diego, Reyes Domínguez, Iván A., Canseco-González, Daniel, Rosales-Vázquez, Luis D., Salomón-Flores, María K., Dorazco-González, Alejandro
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Anions; Aqueous solutions; Ball milling; Carboxylates; Chemical sensors; Chemoreceptors; Energy levels; Energy transfer; Environmental chemistry; Ethanol; Halides; Metal-organic frameworks; Single crystals
• ISSN: 1466-8033; 1466-8033
• DOI: 10.1039/D3CE00434A

Selective anion sensing/recognition by luminescent compounds able to operate in aqueous media is a central topic of supramolecular analytical chemistry that impacts biological and environmental chemistry. In this work, a novel blue-emitting ( λ em = 370 nm) 3D metal–organic framework {[Zn 3 (BDC) 3 (EtOH) 2 ](EtOH) 0.6 } ∞ , Zn-LMOF (BDC = 1,4-benzenedicarboxylate), was synthesized and structurally analysed by single-crystal X-ray diffraction. Subsequently, an Eu( iii )-doped Zn-MOF was obtained using Zn-LMOF by a post-synthetic ball milling reaction, and this compound was studied in detail as a luminescent chemosensor for anions ( e.g. , halides, pseudohalides, oxyanions, and carboxylates) in 20% aqueous ethanol. The new Eu@Zn-LMOF is a hydrostable material with a long-lived pink emission originated by an efficient energy transfer from the excited energy levels of Zn-LMOF toward the 5 D state of Eu( iii ) centers, as evidenced by its strong emission signals at 591, 616, 650, and 698 nm, lifetime ( τ = 0.68 ms), and quantum yield ( Φ PL = 0.32). The addition of anions to aqueous ethanolic dispersions of Eu@Zn-LMOF modified their emission intensities corresponding to Eu( iii ) ions, with a pronounced selectivity and quenching response ( K SV = 7.27 × 10 3 M −1 ) toward F − over common interfering anions such as acetate, phosphate, and heavy halides. The detection limit in the presence of potentially interfering anions is 13.70 μmol L −1 . On the basis of multiple spectroscopic tools, such as SEM-EDS analysis, the optical change is attributed to the efficient release of Eu( iii ) ions from the Zn-LMOF matrix with the simultaneous formation of EuF 3 . These results demonstrate the usefulness of lanthanide-doped Zn-LMOFs as analytical tools for the selective quantification of a neurotoxic and environmental anion in aqueous media.