A pyrazine core-based luminescent Zr(iv) organic framework for specific sensing of Fe3+, picric acid and Cr2O72−. Issue 41 (7th October 2019)

• Record Type: Journal Article
• Authors: Gogoi, Chiranjib; Reinsch, Helge; Biswas, Shyam
• Is Part Of: CrystEngComm. Volume 21:Issue 41(2019)
• Page Start: 6252
• Page End: 6260
• Publication Date: 2019-10-07
• Subjects: Crystals -- Periodicals; Crystal growth -- Periodicals; Crystallography -- Periodicals; Cristaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Cristallographie -- Périodiques; 548
• DOI: 10.1039/c9ce01347d
• Languages: English
• ISSNs: 1466-8033

Abstract

Abstract : A new Zr-MOF incorporating a pyrazine core-based tetracarboxylate was used for selective fluorometric sensing of Fe 3+, picric acid and Cr2 O7 2− with outstanding sensitivity. Abstract : A metal–organic framework (MOF) with a Zr(iv ) ion containing a 2, 3, 5, 6-tetrakis(4-carboxyphenyl)pyrazine (H4 L ) ligand was prepared by a solvothermal method. ZrOCl2 ·8H2 O was employed along with the H4 L ligand and benzoic acid (modulator) in N, N -dimethylformamide (DMF) to synthesize the title compound. The as-synthesized compound has the formula [Zr6 (μ3 -O)4 (μ3 -OH)4 (OH)4 (H2 O)4 (L )2 ]·3H2 O·2DMF (1 ). The activation of 1 was carried out by using methanol exchange and subsequent heating under high vacuum at 130 °C. Both 1 and the activated sample (1′ ) were characterized by X-ray powder diffraction (PXRD), Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA). They displayed high chemical stability and thermal stability. Both 1 and 1′ are stable up to 440 °C. Compound 1′ has a very high BET surface area (1419 m 2 g −E ) and CO2 adsorption capacity (4.4 mmol g −1 at 1.4 bar and 0 °C). Being highly water-stable, luminescent 1′ can selectively recognize Fe 3+ and dichromate (Cr2 O7 2− ) in water and picric acid (PA) in dimethyl sulfoxide (DMSO), by a fluorescence quenching mechanism. The detection limits were found to be 3.75, 13.08 and 8.58 ppb for Fe 3+, PA and Cr2 O7 2−, respectively. Moreover, the mechanisms behind this selective detection of all three analytes were also investigated. In all three cases, the compound showed reusability up to five cycles without any loss of sensing efficacy. These experimental data vividly show that 1′ can be considered as a promising sensing material for Fe 3+, PA and Cr2 O7 2− .