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Updated: Oct 3, 2025

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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Aggregated Structures of Two-Dimensional Covalent Organic Frameworks.

Chengjun Kang1, Zhaoqiang Zhang1, Adam K Usadi2

  • 1Department of Chemical and Biomolecular Engineering, National University of Singapore, 117585, Singapore.

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|February 14, 2022
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Quantifying crystalline phases in 2D Covalent Organic Frameworks (COFs) is challenging. This study utilizes 13C solid-state nuclear magnetic resonance (13C SSNMR) to reveal detailed aggregated structures in COFs, including previously undetected offset stacking.

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Area of Science:

  • Materials Science
  • Solid-State Chemistry
  • Supramolecular Chemistry

Background:

  • Covalent Organic Frameworks (COFs) exhibit diverse crystalline structures, enabling wide applications.
  • Quantifying crystalline phases in polycrystalline 2D COF powders remains a significant challenge.
  • Understanding the aggregated structures of 2D COFs is crucial for optimizing their performance.

Purpose of the Study:

  • To investigate the aggregated structures of 2D Covalent Organic Frameworks (COFs).
  • To explore the utility of 13C solid-state nuclear magnetic resonance (13C SSNMR) for characterizing COF aggregation.
  • To differentiate between various stacking arrangements and their impact on COF properties.

Main Methods:

  • Utilized 13C solid-state nuclear magnetic resonance (13C SSNMR) spectroscopy.
  • Analyzed four distinct 2D COF samples in both dried and solvated states.
  • Correlated spectral changes with different COF layer stacking configurations.

Main Results:

  • Demonstrated that 13C SSNMR can effectively distinguish between different aggregated structures in 2D COFs.
  • Quantitatively differentiated AA stacking from other aggregation types.
  • Identified previously unreported offset stacking structures in 2D COFs, undetectable by X-ray methods.
  • Observed distinct aggregated structures in dried versus solvated COF states.

Conclusions:

  • 13C SSNMR is a powerful tool for quantitative analysis of 2D COF aggregated structures.
  • The study reveals new insights into COF stacking, including short-range ordered offset structures.
  • Findings enhance the understanding of 2D COF structures and pave the way for improved material design and applications.