Multi-responsive luminescent sensor based on Zn (II) metal-organic framework for selective sensing of Cr(III), Cr(VI) ions and p-nitrotolune

Highlights: • A 3D Zn-MOF has been successfully synthesized. • It exhibits highly luminescent sensing properties for Cr³⁺, Cr₂O₇²⁻, p-NP and pH. • The detection limits of Cr³⁺, Cr₂O₇²⁻, and p-NP can reach 5.55 × 10⁻⁶, 6.91 × 10⁻⁶ and 4.01 × 10⁻⁶ M, respectively. • It can be recycled at least four times for sensing Cr³⁺ and Cr₂O₇²⁻ ions. - Abstract: A three-dimensional (3D) zinc metal-organic framework (MOF), {[Zn₂(μ₃-OH)(cpta)(4,4′-bipy)]·H₂O}_n (1) (4,4′-bipy = 4,4′-bipyridine) was solvothermally synthesized base on a semirigid V-shaped multicarboxylate ligand 2–4(-carboxyphenoxy)terephthalic acid (H₃cpta). 1 has a complicated 3D structure in which the tetramer [Zn₄(μ₃-O)₂O₁₀N₄] second building units (SBUs) are interconnected by the V-shaped cpta³⁻ and 4,4′-bipy ligands. 1 shows good selective and sensitive fluorescence sensing effect for detecting Cr(III)/Cr(VI) ions and p-nitrotolune (p-NP). The detection limits of Cr³⁺, Cr₂O₇²⁻, and p-NP can reach 5.55 × 10⁻⁶, 6.91 × 10⁻⁶ and 4.01 × 10⁻⁶ M, respectively. Moreover, 1 can be recycled at least four times for sensing Cr³⁺ and Cr₂O₇²⁻ ions. In addition, the luminescence intensity of 1 is strongly correlated with the pH value in a pH range from 2 to 12.