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Moiré Patterns of Two-Dimensional Covalent Organic Framework Single Crystals Created by Superstacking.

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This study reveals a novel ABCD stacking mode in two-dimensional (2D) covalent organic frameworks (COFs), COF-400. This stacking behavior was observed in derivatives and Moiré patterns, offering new manipulation possibilities for 2D COFs.

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Area of Science:

  • Materials Science
  • Nanotechnology
  • Crystallography

Background:

  • Two-dimensional (2D) covalent organic frameworks (COFs) possess unique molecular and crystalline properties.
  • Understanding the interlayer stacking of 2D COFs is crucial but remains limited.

Purpose of the Study:

  • To report a novel stacking mode in a 2D COF.
  • To investigate the structural characteristics of COF-400 and its derivatives.
  • To explore the superstacking phenomena and Moiré patterns in exfoliated 2D COF films.

Main Methods:

  • Single crystal X-ray and electron diffraction for structural determination.
  • Transmission electron microscopy (TEM) for real-space imaging and high-resolution analysis.
  • Analysis of Moiré patterns in exfoliated COF films with varying twist angles.

Main Results:

  • Discovery of an unprecedented ABCD stacking mode in the 2D COF, COF-400.
  • Inheritance of the ABCD stacking mode in reduced (COF-400-Re) and oxidized (COF-400-Ox) derivatives.
  • Observation of Moiré patterns in superstacked exfoliated COF films, with clear identification of individual 2D COF single crystals.

Conclusions:

  • The findings significantly expand the understanding of 2D COF stacking behaviors.
  • The identified stacking modes offer new avenues for manipulating 2D COFs.
  • These advancements hold potential for future device fabrication applications.