Postsynthetically Modified Covalent Organic Frameworks for Efficient and Effective Mercury Removal

Abstract

A key challenge in environmental remediation is the design of adsorbents bearing an abundance of accessible chelating sites with high affinity, to achieve both rapid uptake and high capacity for the contaminants. Herein, we demonstrate how two-dimensional covalent organic frameworks (COFs) with well-defined mesopore structures display the right combination of properties to serve as a scaffold for decorating coordination sites to create ideal adsorbents. The proof-of-concept design is illustrated by modifying sulfur derivatives on a newly designed vinyl-functionalized mesoporous COF (COF-V) via thiol-ene "click" reaction. Representatively, the material (COF-S-SH) synthesized by treating COF-V with 1,2-ethanedithiol exhibits high efficiency in removing mercury from aqueous solutions and the air, affording Hg and Hg capacities of 1350 and 863 mg g, respectively, surpassing all those of thiol and thioether functionalized materials reported thus far. More significantly, COF-S-SH demonstrates an ultrahigh distribution coefficient value (K) of 2.3 × 10 mL g, which allows it to rapidly reduce the Hg concentration from 5 ppm to less than 0.1 ppb, well below the acceptable limit in drinking water (2 ppb). We attribute the impressive performance to the synergistic effects arising from densely populated chelating groups with a strong binding ability within ordered mesopores that allow rapid diffusion of mercury species throughout the material. X-ray absorption fine structure (XAFS) spectroscopic studies revealed that each Hg is bound exclusively by two S via intramolecular cooperativity in COF-S-SH, further interpreting its excellent affinity. The results presented here thus reveal the exceptional potential of COFs for high-performance environmental remediation.

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.…”

Opportunities of Covalent Organic Frameworks for Advanced Applications

“…2019, 6, 1801410 Figure 14. [62] Copyright 2017, American Chemical Society. For clarity, the extended COF-LZU8 structure is not shown.…”

Recent Advances in Covalent Organic Frameworks for Catalysis

“…The covalentb onding frameworks aree ither homoo rh etero polymerized via organic link- [29][30][31] Somek ey factorsi ncluding temperature, optimal pressure and solvent, et.al could greatly influence the synthesis of COFs. [32][33][34][35] However,t he ionothermal synthesis requires high reaction temperature, which limiting its wide-ranging application.A sa clean and fast synthetic methods, microwave heatings ynthesis offers new facilities for furtherl argescale application. [32][33][34][35] However,t he ionothermal synthesis requires high reaction temperature, which limiting its wide-ranging application.A sa clean and fast synthetic methods, microwave heatings ynthesis offers new facilities for furtherl argescale application.…”