Water-Stable Eu₆-Cluster-Based fcu-MOF with Exposed Vinyl Groups for Ratiometric and Fluorescent Visual Sensing of Hydrogen Sulfide

Abstract

Detection of H2S in the biological system has attracted enormous attention in recent years. In this work, a new vinyl-functionalized metal–organic framework (MOF), [(Me2NH2)2] [Eu6(μ3-OH)8(BDC–CHCH2)6(H2O)6] (Eu-BDC–CHCH2, BDC–CHCH2 = 2-vinylterephthalic acid), was synthesized under solvothermal conditions. The vinyl groups in the ligands can not only modulate the “antenna effect” of the ligand on Eu3+ ions but also serve as an exposed reactive site to allow for the quantitative detection of H2S by Eu-BDC–CHCH2. The ratiometric fluorescent probe has the advantages of water stability, acid-base stability (pH = 2–11), fast response (<2 min), high selectivity, and sensitivity (LOD = 38.4 μM). We also used Eu-BDC–CHCH2 to detect and analyze H2S in tap and lake waters, demonstrating the potential of the probe for biological and environmental applications. In addition, the MOF-based agarose hydrogel film allows for the visual detection of H2S via a smartphone by identifying the RGB values. The vinyl-functionalized MOF can thus be a powerful sensing platform for H2S.

Amino-Functionalized Single-Lanthanide Metal–Organic Framework as a Ratiometric Fluorescent Sensor for Quantitative Visual Detection of Fluoride Ions

“…Strategies employing ligands with the functional groups (e.g., −OH, −NO 2 , −Br, −CH�CH 2 , and −SO 3 ) have been reported to tune the T 1 energy of the ligand and result in the dual-fluorescence emissions in S'LnMOF systems. 35,36 If the introduced functional group can selectively identify the F − ions simultaneously, the detection selectivity of the S'LnMOFs can be readily improved. 37 As is well known, amino is a typical electron-donating group, which can effectively modulate the energy levels of the π-conjugated carboxylate ligand.…”

“…In fact, the luminescence of the S’LnMOF probe depends not only on the intrinsic lowest triplet excited state (T 1 ) energy of the ligand, which directly determines the antenna efficiency, but also on other factors, including the interactions between the host frameworks and the guest species during the sensing process. Strategies employing ligands with the functional groups (e.g., −OH, −NO 2 , −Br, −CHCH 2 , and −SO 3 ) have been reported to tune the T 1 energy of the ligand and result in the dual-fluorescence emissions in S’LnMOF systems. , If the introduced functional group can selectively identify the F – ions simultaneously, the detection selectivity of the S’LnMOFs can be readily improved . As is well known, amino is a typical electron-donating group, which can effectively modulate the energy levels of the π-conjugated carboxylate ligand.…”

A dual-function [Ru(bpy)3]2+ encapsulated metal organic framework for ratiometric Al3+ detection and anticounterfeiting application

“…26,27 By contrast, the fluorescence changes in a sensor based on the fluorescence intensity ratio of two independent emissions (studying the intensity ratio of two independent transitions in a material whose emission spectrum is composed of several bands) can be easily seen by the naked eye. 28–32 In addition, this strategy can reduce the disadvantages of environmental effect interference of monochromatic light-emitting MOF sensors. In this regard, porous PL MOFs, which have abundant active sites for incorporating other chromophore molecules, have gained intensive application prospects in the field of colorimetric fluorescence sensing.…”

A Highly Selective MOF-Based Probe for Turn-On Luminescent Detection of Al3+, Cr3+, and Fe3+ in Solution and Test Paper Strips through Absorbance Caused Enhancement Mechanism

“…In the regime of porous materials, − metal–organic frameworks (MOFs) have evolved as a new class of luminescent sensors for fast detection of metal cations, anions, nitro-explosives, organic solvents, protons, etc., and these materials usually score over their contemporary competitors, because of rich structural diversity, high surface area, porosity, tunability and possibility of near infinite combinations of metal/metal clusters and ligands. − In addition, other advantages associated with MOF-based luminescent sensors include ease of use, low cost of operation, very high sensitivity, selectivity and recyclability, etc. − Rational and judicious choice of different types of ligands and their fruitful combination through mixed-ligand synthesis approach has dictated the construction of MOFs with admirable framework structures. Nevertheless, this strategy has been widely used for the construction of multifunctional MOFs, developing luminescent metal–organic framework (LMOF) based sensors using such a strategy has been rarely explored. − The research on LMOFs has repeatedly highlighted the significant roles of Lewis basic sites such as unsaturated pyridyl groups, free −NH 2 groups, uncoordinated −OH groups, and other uncoordinated N-rich sites etc.…”