Thioether Side Chains Improve the Stability, Fluorescence, and Metal Uptake of a Metal–Organic Framework

Abstract

This work builds on the recently developed hardÀsoft approach, as is embodied in the carboxylÀthioether combination, for functionalizing metalÀorganic frameworks (MOFs), and it aims to further demonstrate its efficacy and generality in connection with the prototypic MOF-5 system [i.e., Zn 4 O(bdc) 3 , where bdc is 1,4-benzene dicarboxylate]. Specifically, the thioether side chain CH 3 SCH 2 CH 2 SÀ (methylthioethylenethio, or MSES) is placed at the 2,5-positions of bdc, and the resultant molecule (L) was crystallized with Zn(II) ions into a porous, cubic network [Zn 4 O(L) 3 ] topologically equivalent to MOF-5. Compared with the previously used methylthio (CH 3 SÀ) group, the MSES side chain is more flexible, has more S atoms as the binding sites (per chain), and extends further into the channel region; therefore, this side chain is predisposed for more-efficient binding to soft metal species when installed in a porous MOF matrix. Here, we report the significantly improved properties, with regard to stability to moisture, fluorescence intensity, and capability of metal uptake. For example, activated solid samples of 1 feature long-term stability (more than 3 weeks) in air, have a notable sensing response to nitrobenzene (in the form of fluorescence quenching), and are capable of taking up HgCl 2 from an ethanol solution at a concentration as low as 84 mg/L.

Fine-tuning of the confined space in microporous metal–organic frameworks for efficient mercury removal

“…ICP and SEM/EDX analyses, combined with single crystal Xray diffraction, confirmed that compound 1 is capable to capture HgCl 2 from aqueous solution as other MOFs [38][39][40][41][42][43][44]57 and COFs, 33,58,59 through the abovementioned dual step capture process to give 0.5HgCl 2 @1 and HgCl 2 @1. The HgCl 2 loading, even in the case of HgCl 2 @1 (ca.…”

“…S11). ] in contaminated aqueous solutions and the time required to achieve such decrease for 1 (red), and different materials reported such as MOFs [38][39][40][41][42][43][44] (green), COFs 33,58,59 (covalent-organic frameworks, blue), POPs 31,32,61 (porous organic polymers, orange), mesoporous silicas 62 (purple) and chalcogels 63 (cyan). Dashed line represent the frontier between contaminated and accepted limits for drinking water.…”

Mercury nano-trap for effective and efficient removal of mercury(II) from aqueous solution

“…8). This represents an advantage of PAF-1-SH for mercury removal across a wide range of pH, particularly when compared with silica and MOFs based adsorbents [12][13][14][15][16][29][30][31][32][33][34] , which usually suffer from the loss of porosity under such harsh conditions. Mercury adsorption experiments under acid and basic conditions revealed that PAF-1-SH also exhibits high affinities for Hg(II) with K d values of 6.66 Â 10 7 ml g À 1 at pH 1.0 and 2.49 Â 10 7 ml g À 1 at pH 12.8, which render excellent capability of reducing Hg(II) concentrations from 10 p.p.m.…”

“…Thiol/thio-functionalized adsorbents, including clays 10 , resins 11 , mesoporous silica [12][13][14][15][16] , activated carbons 17 , mesorporous carbons 18 and chalcogenides 19,20 , are considered very effective sorbents for Hg(II) removal from aqueous solutions due to the soft-soft interaction 21 . Recently, metal-organic frameworks (MOFs) [22][23][24][25][26][27][28] have been explored as a new type of adsorbents for mercury removal [29][30][31][32][33][34] due to their high surface areas, but they usually suffer from instability in water 29,30 or aqueous solutions with a wide pH range 34 and possess low adsorption capacity and weak affinity for Hg(II).…”

Syntheses, structures and tunable luminescence of lanthanide metal-organic frameworks based on azole-containing carboxylic acid ligand

“…They are promising as light emitting materials with a wide range of colors provided by inorganic metal centers, organic linkers, guest solvent molecules, as well as metal-organic charge transfer [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. In addition, the emitted color can also be readily modulated by different lanthanide ions and their concentrations, guest species, and excitation wavelengths [37][38][39][40][41].…”