A new 3D four-fold interpenetrated dia-like luminescent Zn(ii)-based metal–organic framework: the sensitive detection of Fe3+, Cr2O72−, and CrO42− in water, and nitrobenzene in ethanol

Abstract

A new three-dimensional zinc-based metal–organic framework, namely [Zn₂(4,4′-nba)₂(1,4-bib)₂]_n (1), where 4,4′-H₂nba = 3-nitro-4,4′-biphenyldicarboxylic acid and 1,4-bib = 1,4-bis(imidazole-1-ylmethyl)benzene, has been solvothermally synthesized and structurally characterized via single-crystal X-ray diffraction, IR spectroscopic, elemental, thermogravimetric, and Hirshfeld surface analyses. In the crystal structure of 1, the oxygen and nitrogen atoms of two 4,4′-nba²⁻ and two 1,4-bib ligands bind to the metal ion, creating irregular tetrahedral geometry. The 4,4′-nba²⁻ and 1,4-bib ligands serve as linear bidentate linkers to form a four-fold interpenetrated 3D framework with dia-like topology. Luminescence studies revealed that 1 can be used as a highly sensitive multi-responsive luminescent sensor for sensing Fe³⁺, Cr₂O₇²⁻, and CrO₄²⁻ in H₂O, and nitrobenzene in C₂H₅OH. The detection limits of Fe³⁺, Cr₂O₇²⁻, CrO₄²⁻ and nitrobenzene can reach 1.76 μM, 3.25 μM, 3.8 μM and 0.19 μM, respectively. Moreover, 1 can be recycled at least five times for sensing Fe(III) and Cr(VI). The sensitivity and stability of 1, 1@Fe³⁺, 1@Cr₂O₇², and 1@CrO₄²⁻ were also investigated at different pH and temperature values. 1 exhibited satisfactory sensing abilities when the pH ranged from 3 to 10, and the temperature ranged from 5 °C to 75 °C, indicating that 1 could act as a fluorescent probe for Fe³⁺ under physiological pH conditions. These results support the idea that 1 has good anti-interference abilities and potential for sensing Fe(III), Cr(VI) and nitrobenzene in real environments. In addition, the possible fluorescence quenching mechanism was explored in this paper.