Trace Quantity Detection of H2PO4− by Fluorescent Metal Organic Framework (F-MOF) and Bio-Imaging Study

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, Nʹ-diisonicotinoyl-2-hydroxy-5-methyl-isophthalaldehyde dihydrazone) is used for selective recognition of H2PO4− anion by ‘turn-off’ fluorescent sensing technique. Single-crystal X-ray analysis accounts that the asymmetric unit is constituted of two different Zn(II) centres by PCDF–INH and the bridging group, BDC2− ions are responsible for the generation of helical polymer and the biporous structures (14.807×13.096 A2 and 24.905×24.932 A2). 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 fifteen different anions including different phosphates (PO43−, HPO42−, P2O74−). The entire sensing activity of 1 is examined by spectrofluorometric method, 1H–NMR titration, PXRD analysis, bio-imaging study, and the limit of detection is 3.903 μM. However, in vitro bio-sensing analysis confers that F-MOF (1) is sensible toward the H2PO4− ion at a trace level in the human lung fibroblast cells and human liver cancer cell line Hep G2.