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3D Covalent Organic Frameworks Selectively Crystallized through Conformational Design.

Ha L Nguyen1,2, Cornelius Gropp1, Yanhang Ma3

  • 1Department of Chemistry, University of California Berkeley; Kavli Energy Nanoscience Institute at UC Berkeley; and Berkeley Global Science Institute, Berkeley, California 94720, United States.

Journal of the American Chemical Society
|November 13, 2020
PubMed
Summary
This summary is machine-generated.

Researchers designed triangle and square building units to selectively form crystalline imine covalent organic frameworks (COFs) with high surface area. This conformational control is key to achieving the desired fjh topology and material properties.

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Area of Science:

  • Materials Science
  • Chemistry
  • Nanotechnology

Background:

  • Covalent organic frameworks (COFs) are crystalline porous polymers with tunable properties.
  • Selective synthesis of COFs with specific topologies and high crystallinity remains a challenge.
  • Controlling the conformation of building units is crucial for directed framework assembly.

Purpose of the Study:

  • To develop a strategy for the selective formation of imine COFs with the fjh topology.
  • To investigate the role of building unit conformation in COF crystallization.
  • To synthesize and characterize new COFs with high surface areas.

Main Methods:

  • Conformational design of triangle (TTFB) and square (ETTA) building units.
  • Reticulation of designed units to form imine COFs.
  • Characterization using spectroscopic, microscopic, and X-ray diffraction techniques.
  • Porosity and surface area analysis using BET method.

Main Results:

  • Selective formation of a crystalline imine COF, COF-790, with the fjh topology was achieved.
  • COF-790 exhibits a high Brunauer-Emmett-Teller (BET) surface area of 2650 m² g⁻¹.
  • Pre-designed conformations of building units (dihedral angles 75-90°) were critical for crystalline product formation.
  • Two isoreticular COFs (COF-791 and COF-792) were synthesized using alternative square units.

Conclusions:

  • Conformational control of building units is a powerful strategy for selective COF synthesis.
  • The developed method allows for the rational design of crystalline COFs with specific topologies.
  • The synthesized COFs possess high porosity and surface area, indicating potential applications in gas storage and separation.