Trace Quantity Detection of H₂PO₄^– by Fluorescent Metal–Organic Framework (F-MOF) and Bioimaging Study

Abstract

Drinking water quality management and sustainable environment to water bodies are a major concern to public health engineering departments. Inorganic phosphate (Pi), one of the major inorganic pollutants, is addressed for the last two decades regarding trace quantity detection. Over the past few years, a large number of fluorescent metal–organic frameworks (F-MOFs) have been studied to explore the desirable method for selective water analysis. In this article, a Zn(II) 3D F-MOF, {[Zn2(PCDF-INH)(BDC)2]·(H2O)}n (1) (H2BDC = 1,4-benzenedicarboxylic acid, and PCDF-INH = N,N′-diisonicotinoyl-2-hydroxy-5-methyl-isophthalaldehyde dihydrazone), is used for selective recognition of H2PO4– anion by a “turn-off” fluorescent sensing technique. Single-crystal X-ray analysis accounts that the asymmetric unit is constituted of two different Zn(II) centers by PCDF-INH, and the bridging group BDC2– ions are responsible for the generation of the helical polymer and the biporous structures (14.807 × 13.096 Å2 and 24.905 × 24.932 Å2). The compound, 1, exhibits strong emission at 505 nm in CH3OH–H2O solution and is “turn-off” upon the addition of H2PO4–. The selectivity and specificity for H2PO4– have been checked in the presence of 15 different anions, including different phosphates (PO43–, HPO42–, P2O74–). The entire sensing activity of 1 is examined by spectrofluorometric method, 1H NMR titration, PXRD analysis, and bioimaging study, and the limit of detection is 3.903 μM. However, in vitro biosensing analysis confers that F-MOF (1) is sensable toward the H2PO4– ion at a trace level in the human lung fibroblast cells and human liver cancer cell line Hep G2.