Luminescent Metal–Organic Framework Sensor: Exceptional Cd²⁺ Turn‐On Detection and First In Situ Visualization of Cd²⁺ Ion Diffusion into a Crystal

Abstract

With regard to fluorescence quenching commonly observed during metal-ion detection, "turn-on" chemical sensing has been rarely reported, but could be extremely important because it facilitates the selective recognition of target objects of interest against a dark background. A metal-organic framework (MOF) chemosensor has been prepared that serves as an efficient platform for the selective detection of Cu and Cd ions over other metal ions. In particular, this framework shows the highest fluorescence enhancement (≈60-fold relative to Cd-free MOF) for the hazardous metal ion Cd among luminescent MOFs and displays excellent reusability in repeated cycles. The direct diffusion of Cd into the crystal pores has also been visualized for the first time.

Enzyme‐Assisted Metal–Organic Framework Sensing System for Diethylstilbestrol Detection

“…PowderX -ray diffraction (PXRD) analysis (Figure 1a) showedt hat this compound presents aU iO-type connection with all the diffraction peaks and it could be readily indexed to [Zr 6 O 4 (OH) 4 (sbdc) 6 ], ar ecently reported membero ft his MOF series. [19] This backbone structure was also supported by elemental and thermogravimetric analyses ( Figure S1 in the Supporting Information), which determined the formula of [Zr 6 O 4 (OH) 4 (sbdc) 6 ](DMF) 3 (H 2 O) 30 .U iO-typeM OFs are famous for the high stability and extensive channel structure. The N 2 adsorption experiment of our sample gave the pore volume of 1.05 cm 3 g À1 and BETs urface area of 2080 m 2 g À1 ( Figure S2 in the Supporting Information).…”

“…ZrOCl 2 ·8 H 2 O( 96.7 mg, 0.3 mmol) and H 2 sbdc (80.5 mg, 0.3 mmol) were dissolved in am ixed solvent of DMF (21 mL) and acetic acid (7 mL) and heated at 120 8Cf or 8h with continuous stirring. After cooling down to room temperature, the white precipitate of Zrsbdc was separated by centrifugation, washed with DMF and methanol in sequence, and then dried in vacuum at 80 8Cf or 6h; elemental analysis calcd (%) for [Zr 6 O 4 (OH) 4 (sbdc) 6 ](DMF) 3…”

“…The wide choice of metal ions and organic linkers makes the optical properties of MOFs highly tunable, and their channel structures could serve as a powerful tool for analyte screening and enrichment in the sensing process. However, most of the researches in this area are focused on the detection of traditional pollutants, such as, nitro compounds, heavy metal ions, and VOCs, whereas the applications of MOFs to the analysis of the pollutants with more complicated structures are still very rare yet . Over the last few decades, the occurrence of endocrine disrupting chemicals (EDCs), which could be defined as the compounds that have potential adverse effects on body through interactions with the endocrine system, has become a worldwide issue of increasing environmental concern .…”

Insights into the Fluorescence Sensing Mechanism of Scandium‐Based Metal‐Organic Frameworks by Solid‐State NMR Spectroscopy

“…To our surprise, the binding energies (N 1s peak) in Figure S2b of N atom in the ligand was invariant upon capture of Ni 2+ /Co 2+ ions, because the amino group N atom of the ligand is supposed to be accessible to the foreign metal ions . The reason might be that the amino group N atom of the ligand is sterically congested in the coordination structure, and is difficult to interact with the foreign metal ions …”

“…Luminescence in MOFs mainly comes from the building components, and the luminescence of the organic linkers and metal nodes is the most important . When guest analytes enter into the cavities of a host framework and interact with the active sites on the framework, thus the emission characteristics are changed with regard to the guest‐free host material . Fluorescence quenching or enhancement through host‐guest interactions usually acts as the signal transduction mechanism for chemical sensing.…”