Hydrogen-bonding and π-π interaction promoted solution-processable covalent organic frameworks

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Covalent organic frameworks (COFs) exhibit significant potential across diverse applications including gas separation, biomedicine, sensing, and printing.
• A major limitation for COF utilization is their poor solubility in common solvents, hindering practical implementation.
• Developing processable COFs is crucial for unlocking their full application spectrum.

Purpose of the Study:

• To develop a facile top-down method for creating solution-processable covalent organic frameworks.
• To enable the fabrication of COF-based inks for direct surface printing applications.
• To elucidate the interactions responsible for COF dispersibility in ionic liquids.

Main Methods:

• Utilizing ionic liquids, specifically 1-methyl-3-octylimidazolium bromide, to achieve COF dispersion.
• Employing heat treatment to homogenize bulk COF powders in ionic liquids, forming stable colloids.
• Characterizing the resulting COF colloids for ink formulation and printing.
• Conducting molecular dynamics and quantum mechanical calculations to understand interaction mechanisms.

Main Results:

• Successfully dispersed imine-linked, azine-linked, and β-ketoenamine linked COFs in an ionic liquid.
• Created high-concentration COF colloids that can be formulated into printable inks.
• Demonstrated direct printing of COF materials onto surfaces using the developed inks.
• Computational studies indicated that C‒H···π and π-π interactions between ionic liquid cations and COFs facilitate colloidal solution formation.

Conclusions:

• A convenient top-down approach has been established for producing solution-processable covalent organic frameworks.
• The developed method overcomes the processability challenges of COFs, paving the way for their practical application.
• This work provides a scalable strategy for fabricating COF inks, enabling advanced material printing and device fabrication.