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Zn (II) /Cd (II) -based dual ligand Luminescent Metal–Organic Frameworks (LMOFs) M (ATA) (L) n · x H 2 O (1) and (2) were synthesized by versatile synthetic routes, viz. , diffusion of precursor solutions, conventional reflux, and green mechanochemical (grinding) reactions from bipyridyl-based Schiff base, (E) - N ′- (pyridin-4-ylmethylene) isonicotinohydrazide (L) and amino functionalized 2-aminoterephthalic acid (H 2 ATA) as linkers. Chemical and thermal stability, phase purity, and characterization of both LMOFs were established by various analytical methods. SXRD analysis revealed the 3D framework is composed of two-dimensional M (ATA) n nets doubly pillared by L through the terminal nitrogen atom. Selective and sensitive detection of chromate anions (CrO 4 2– /Cr 2 O 7 2–) and Fe 3+ /Pd 2+ cations in the aqueous phase by fluorescent quenching of the LMOFs 1 and 2 has been established. Competitive experiments in the presence of interfering anions/cations with 1 and 2 revealed no major change in the quenching efficiency. The observed limits of detection (LOD) values by 1 for CrO 4 2– /Cr 2 O 7 2– were 0. 25 μM (48 ppb) /0. 43 μM (126 ppb) and for Fe 3+ /Pd 2+ were 3. 76 μM (0. 61 ppm) /0. 20 μM (35 ppb), whereas LOD values by 2 were 0. 18 μM (35 ppb) /0. 19 μM (55 ppb) and 1. 77 μM (0. 29 ppm) /0. 10 μM (18 ppb), respectively. Simple fluorescent-based test paper strips have been developed for reliable and visual detection of the mentioned analytes in practical applications. The present investigation clearly demonstrates selective detection of CrO 4 2– /Cr 2 O 7 2– and Fe 3+ /Pd 2+ in aqueous media, and the probable mechanism for the quenching phenomena based on structural aspects has also been discussed.
Parmar et al. (Tue,) studied this question.