Two robust Zn(ii)-organic frameworks as dual-functional fluorescent probes for efficient sensing of enrofloxacin and MnO ₄ ⁻ anions

Abstract

Two robust Zn-MOFs were employed as visual and ultra-sensitive indicators toward enrofloxacin (ENR) and MnO ₄ ⁻ anions in aqueous phase.

Abstract

Selective detection of antibiotics and MnO ₄ ⁻ is crucial for human health improvement and protecting the environment. Two stable Zn( ii)-based metal–organic frameworks (MOFs) {[Zn ₆(L1) ₂(NDC) ₅( μ ₂-OH) ₂]·0.5H ₂O} _n (1), and {[Zn(L2)(NDC)]·2H ₂O} _n (2) (H ₂NDC = 1,4-naphthalenedicarboxylic acid, L1 = 1,5-bis(1-(pyridine-4-ylmethyl)-1 H-benzo[ d]imidazol-2-yl)pentane, L2 = 1,6-bis(1-(pyridine-4-ylmethyl)-1 H-benzo[ d]imidazol-2-yl)hexane) were successfully synthesized by adopting the mixed ligands approach. 1 is a rare 3D 3, 5, 6T23 framework based polynuclear complex group. 2 possesses a 2D sql layer. The two MOFs exhibit excellent chemical and thermal stability. The title compounds are promising dual-functional fluorescent sensors for detecting enrofloxacin/MnO ₄ ⁻ anions with high selectivity and sensitivity ( K _sv values toward enrofloxacin: 4.29 × 10 ⁶ L mol ⁻¹ for 1 and 4.59 × 10 ⁶ L mol ⁻¹ for 2 and toward MnO ₄ ⁻: 1.05 × 10 ⁴ for 1, 5.48 × 10 ³ L mol ⁻¹ for 2, respectively), which are the first observations of fluorescent MOFs for the sensing of enrofloxacin and MnO ₄ ⁻ anions.