Synthesis and crystal structure of a Zn(II) metal-organic framework based on 1,3,5-benzenetricarboxylate and 4,4′-bis(1-imidazolyl)biphenyl ligands: selective sensing of Mn²⁺ and Fe³⁺ ions in aqueous solution

Abstract

A new metal-organic framework (MOF), {[Zn₃(btc)₂(bimb)₂(H₂O)₂](H₂O)₃} _n (1), where H₃btc =1,3,5-benzenetricarboxylate and bimb = 4,4′-bis(1-imidazolyl)biphenyl, has been synthesized and characterized using single-crystal X-ray diffraction, IR spectroscopy, elemental, thermogravimetric, and photoluminescent analysis. X-ray diffraction crystallographic analyses indicate that 1 displays two types of Zn centers with a distorted pyramidal and a perfectly octahedral coordination sphere. The fully deprotonated btc³⁻ ligand coordinates four Zn ions with two carboxylate groups having bidentate chelate modes and one binds µ ₂-η ¹:η ¹; bimb serves as a μ ₂-bridging ligand in 1, resulting in a new three-dimensional (3-D) metal-organic framework with an uncommon trinodal 4-connected network with a Schäfli symbol of (6⁵ 10)₂(6² 8 10³)₃(7³ 8 12) topology. In the crystal, a 3-D supramolecular architecture is further formed by O–H···O hydrogen bonds, C–H···O interactions, C–H···π as well as π···π stacking. 1 shows intense fluorescence in the solid state and exhibits high selectivity for Mn²⁺ and Fe³⁺ ions through fluorescence enhancement and the quenching effect in aqueous solutions at room temperature, respectively.

Graphical Abstract

Keywords:

• Metal-organic frameworks
• Luminescence properties
• Fluorescence enhancement effect
• Fluorescence quenching effect
• Crystal structure

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The support of the National Natural Science Foundation of China (No. 51402158) is gratefully acknowledged. The authors also acknowledge financial support from the Natural Science Foundation of Qinzhou University (No. 2016PY-GJ01) and the Opening Project of Guangxi Colleges and Universities Key Laboratory of Beibu Gulf Oil and Natural Gas Resource Effective Utilization (No. 2017KLOG11).