Two robust Zn(ii)-organic frameworks as dual-functional fluorescent probes for efficient sensing of enrofloxacin and MnO4− anions

Abstract

Selective detection of antibiotics and MnO₄⁻ is crucial for human health improvement and protecting the environment. Two stable Zn(II)-based metal–organic frameworks (MOFs) {[Zn₆(L1)₂(NDC)₅(μ₂-OH)₂]·0.5H₂O}_n (1), and {[Zn(L2)(NDC)]·2H₂O}_n (2) (H₂NDC = 1,4-naphthalenedicarboxylic acid, L1 = 1,5-bis(1-(pyridine-4-ylmethyl)-1H-benzo[d]imidazol-2-yl)pentane, L2 = 1,6-bis(1-(pyridine-4-ylmethyl)-1H-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/MnO₄⁻ anions with high selectivity and sensitivity (K_sv values toward enrofloxacin: 4.29 × 10⁶ L mol⁻¹ for 1 and 4.59 × 10⁶ L mol⁻¹ for 2 and toward MnO₄⁻: 1.05 × 10⁴ for 1, 5.48 × 10³ L mol⁻¹ for 2, respectively), which are the first observations of fluorescent MOFs for the sensing of enrofloxacin and MnO₄⁻ anions.