Luminescent Zn(II) Coordination Polymers for Highly Selective Sensing of Cr(III) and Cr(VI) in Water

Abstract

Three photoluminescent zinc coordination polymers (CPs), {[Zn(tpeb)(2,5-tdc)(2,5-Htdc)]·2HO} (1), {[Zn(tpeb)(1,4-ndc)(1,4-Hndc)]·2.6HO} (2), and {[Zn(tpeb)(2,3-ndc)]·HO} (3) (tpeb = 1,3,5-tri-4-pyridyl-1,2-ethenylbenzene, 2,5-tdc = 2,5-thiophenedicarboxylic acid, 1,4-ndc = 1,4-naphthalenedicarboxylic acid, and 2,3-ndc = 2,3-naphthalenedicarboxylic acid) were prepared from reactions of Zn(NO)·6HO with tpeb and 2,5-Htdc, 1,4-Hndc, or 2,3-Hndc under solvothermal conditions. Compound 1 has a two-dimensional (2D) grid-like network formed from bridging 1D [Zn(tpeb)] chains via 2,5-tdc dianions. 2 and 3 possess similar one-dimensional (1D) double-chain structures derived from bridging the [Zn(tpeb)] chains via pairs of 1,4-ndc or 2,3-ndc ligands. The solid-state, visible emission by 1-3 was quenched by Cr, CrO, and CrO ions in water with detection limits by the most responsive complex 3 of 0.88 ppb for Cr and 2.623 ppb for CrO (pH = 3) or 1.734 ppb for CrO (pH = 12). These values are well below the permissible limits set by the USEPA and European Union and the lowest so far reported for any bi/trifunctional CPs sensors. The mechanism of Cr luminescence quenching involves irreversible coordination to free pyridyl sites in the CP framework, while the Cr quenching involves reversible overlap of the absorption bands of the analytes with those of the excitation and/or emission bands for 3.

A Recyclable bi‐functional Luminescent Zinc (II) metal–organic framework as highly selective and sensitive sensing probe for nitroaromatic explosives and Fe3+ ions

“…The quenching efficiency for various nitroaromatics were plotted in Figure . The detection limit of the Zn‐MOF as a luminescent probe for detecting NPLR solution was found to be 1.71 ppb, which is supported by the calculated results based on the equation: detection limit = 3δ/k (δ is the standard deviation of blank measurement; k is the slope between the luminescence intensity vs. log[NPLR] (Figure ). Bappaditya Gole et al had synthesized several MOFs to sense TNT as a level as 3.63 ppb .…”

Water‐Stable Luminescent Zn(II) Metal‐Organic Framework as Rare Multifunctional Sensor for Cr(VI) and TNP

“…To check whether the energy‐transfer caused the observed quenching effect, we performed an experiment of simplified fluorescent analysis (Figure a) . The suspension of 1 in water was placed in a quartz cell (position B), while the solution of Cr 2 O 7 2− (1×10 −2 M) or CrO 4 2− (1×10 −2 M) was placed in the excitation path (position A) and emission path (position C), then we detected the fluorescence intensity.…”

CdII‐Organic Frameworks Fabricated with a N‐Rich Ligand and Flexible Dicarboxylates: Structural Diversity and Multi‐Responsive Luminescent Sensing for Toxic Anions and Ethylenediamine

“…[16] The PXRD patterns display that complexes 1-3 have almost no change before and after immersed in Cr 2 O 7 2À or MnO 4 À ,a nd the weights after the treatment of DMF/DMA( complex 1 in DMF and complex 2 or 3 in DMA, respectively) were characterizeda nd the results showed that there were almost no loss of the mass, [29] which implying that the main framework structures of 1-3 stillm aintain (Figure S5 a-S7). Both Cr 2 O 7 2À and MnO 4 À have wide absorption bands in the UV-vis area, [30,31] and there is overlap betweent he absorption bands of Cr 2 O 7 2À /MnO 4 À and the excitation of 1-3, which implying that Cr 2 O 7 2À /MnO 4 À may conceal the absorption of excitation energy and give rise to the fluorescence quenching. In addition, the interactions between anions and complexes may also lead to the quenching effect.…”