Postsynthetically Modified Covalent Organic Frameworks for Efficient and Effective Mercury Removal.
Qi Sun1, Briana Aguila1, Jason Perman1
1Department of Chemistry, University of South Florida , 4202 East Fowler Avenue, Tampa, Florida 33620, United States.
Journal of the American Chemical Society
|February 23, 2017
Summary
New covalent organic frameworks (COFs) offer superior mercury removal. These advanced materials efficiently capture mercury from water and air, showcasing high capacity and affinity for environmental remediation applications.
Area of Science:
- Materials Science
- Environmental Science
- Chemistry
Background:
- Designing effective adsorbents for environmental remediation requires high affinity chelating sites for rapid contaminant uptake and capacity.
- Two-dimensional covalent organic frameworks (COFs) offer tunable structures and porosity, making them promising scaffolds for adsorbent development.
Purpose of the Study:
- To design and synthesize a novel mesoporous COF functionalized with sulfur derivatives for efficient mercury removal.
- To evaluate the adsorption capacity, affinity, and mechanism of the functionalized COF for mercury species (Hg²⁺ and Hg⁰).
Main Methods:
- Synthesis of a vinyl-functionalized mesoporous COF (COF-V) followed by modification with 1,2-ethanedithiol via thiol-ene click reaction to yield COF-S-SH.
- Testing the adsorption performance of COF-S-SH for Hg²⁺ and Hg⁰ in aqueous solutions and air.
- Characterization using X-ray absorption fine structure (XAFS) spectroscopy to elucidate the mercury binding mechanism.
Main Results:
- The synthesized COF-S-SH exhibited exceptional Hg²⁺ and Hg⁰ adsorption capacities of 1350 and 863 mg g⁻¹, respectively, exceeding existing thiol-functionalized materials.
- Achieved an ultrahigh distribution coefficient (Kd) of 2.3 × 10⁹ mL g⁻¹, rapidly reducing Hg²⁺ concentration below drinking water limits.
- XAFS analysis revealed exclusive Hg binding by two sulfur atoms via intramolecular cooperativity, explaining the strong affinity.
Conclusions:
- Mesoporous COFs decorated with sulfur chelating groups are highly effective adsorbents for mercury remediation.
- The ordered structure and high density of binding sites in COFs contribute to superior adsorption performance and rapid diffusion.
- This study highlights the significant potential of COFs for developing advanced materials for high-performance environmental remediation.
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