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Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface
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Isostructural Three-Dimensional Covalent Organic Frameworks.

Chao Gao1, Jian Li2,3, Sheng Yin1

  • 1Sauvage Center for Molecular Sciences and Key Laboratory of Biomedical Polymers (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, China.

Angewandte Chemie (International Ed. in English)
|May 21, 2019
PubMed
Summary
This summary is machine-generated.

Researchers synthesized three isostructural 3D covalent organic frameworks (COFs) with varying functional groups. Continuous rotation electron diffraction (cRED) allowed atomic-level structural determination for the first time, revealing tunable CO2/N2 selectivity.

Keywords:
continuous rotation electron diffractioncovalent organic 3D frameworksgas separationstructure elucidation

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Area of Science:

  • Materials Science
  • Crystallography
  • Supramolecular Chemistry

Background:

  • Covalent Organic Frameworks (COFs) are crystalline porous polymers with tunable properties.
  • Determining the atomic structure of polycrystalline COFs has been challenging.
  • Functional group modification is key to tailoring COF properties for specific applications.

Purpose of the Study:

  • To synthesize and characterize isostructural 3D COFs with different substituents (-H, -Me, -F).
  • To determine the crystal structures of these 3D COFs at atomic resolution using continuous rotation electron diffraction (cRED).
  • To investigate the effect of pore environment modification on gas selectivity (CO2 over N2).

Main Methods:

  • Designed synthesis of three isostructural 3D COFs.
  • Crystal structure determination using continuous rotation electron diffraction (cRED).
  • Gas adsorption/selectivity measurements (CO2/N2).

Main Results:

  • Three isostructural 3D COFs with similar crystallinity and topology were successfully synthesized.
  • The crystal structures revealed a fivefold interpenetrated pts topology.
  • Atomic resolution (0.9-1.0 Å) was achieved by cRED, enabling direct localization of all non-hydrogen atoms in a COF framework for the first time.
  • Varying substituents (-H, -Me, -F) precisely controlled pore environments, leading to differential CO2/N2 selectivities.

Conclusions:

  • Polycrystalline COFs can be studied at the atomic level using advanced diffraction techniques.
  • cRED is a powerful tool for elucidating the precise atomic structures of COFs.
  • Tailoring pore environments through functional group engineering in 3D COFs is effective for achieving selective gas separation.