Water-Robust Zinc–Organic Framework with Mixed
Nodes and Its Handy Mixed-Matrix Membrane for Highly Effective Luminescent
Detection of Fe3+, CrO42–,
and Cr2O72– in Aqueous Solution
Metal–organic
frameworks (MOFs) and MOF-based composites
as luminescent sensors with excellent economic practicability and
handy operability have attracted much attention. Herein, we designed
and fabricated a porous Zn-based MOF, [Zn(OBA)2(L1)·2DMA]n [1; H2OBA = 4,4′-oxybis(benzoic acid), L1 = 2,4,6-tris(4-pyridyl)pyridine,
and DMA = N,N-dimethylacetamide],
with mixed nodes under solvothermal conditions, and the pore size
of 5.9 Å was calculated from N2 adsorption isotherms
by using a density functional theory model. The as-synthesized compound 1 is stable in different boiling organic solvents and water
solutions with a wide pH range of 2–12 and exhibits intense
luminescence emission at 360 nm under excitation of 290 nm. Significantly,
compound 1 shows high selective detection of Fe3+, CrO42–, and Cr2O72– in aqueous solution even under the interference
of other ions. Compound 1 can quickly sense these ions
in a short time and has a striking sensitivity toward Fe3+ with an ultralow limit of detection (LOD) of 1.06 μM. The
relatively low LODs for CrO42– and Cr2O72– are 3.87 and 2.37 μM,
respectively, compared to the reported works. Meanwhile, compound 1 can be reused to detect Fe3+, CrO42–, and Cr2O72– six times by simple regeneration. Considering the practicability,
a mixed-matrix membrane (MMM) incorporated compound 1 and poly(methyl methacrylate) has been constructed. This MMM displays
quick detection of Fe3+, CrO42–, and Cr2O72– and prompt
regeneration by lifting from the analyte. This useful MMM shows a
comparable LOD below 4.35 μM for these ions. This work presents
a cost-effective Zn-based MOF as a functional platform for simple
but useful sensing of Fe3+, CrO42–, and Cr2O72– in aqueous
solution.