Two bis-color excited luminescent sensors of two-dimensional Cd(II)-MOFs bearing mixed ligands for detection of ions and pesticides in aqueous solutions

Abstract

Two metal organic framework were constructed from mix-ligands and Cd(II) ions: [Cd(NIP)2(DTP)(H2O)2]·H2O (Cd-1) (H2NIP = 5-nitroisophthalic acid and DTP = 3,5-di(1,2,4-triazol-1-yl)pyridine) and [Cd(NTP)2(DTP)(Et)(H2O)2]·(H2O)0.5 (Cd-2) (H2NTP = nitroterephthalic acid and Et = ethanol). The MOFs were determined and confirmed by single-crystal X-ray diffraction (XRD), elemental analysis, infrared spectroscopy (IR), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and fluorescence analysis. The fluorescence sensing application of the sensors demonstrated the two sensors were extra sensitive and selective towards Fe3+ and Cr2O72- during the sensing of the ions under both 250 and 290 nm excitation wavelength; were extra effective and sensitive towards NTP (EX 250 nm) and MMT (EX 290 nm) in sensing of the pesticides for the two sensors. Mechanism investigation revealed both inner filter effect (IFE) and fluorescence resonance energy transfer (FRET) mechanisms played major roles during the sensing process of Fe3+, Cr2O72−, NTP and MMT.