Interlayer Interactions as Design Tool for Large-Pore COFs.

Area of Science:

• Materials Science
• Chemistry

Background:

• Large-pore covalent organic frameworks (COFs) exceeding 5 nm pore size are rare due to synthesis challenges.
• Pore occlusion and collapse are significant hurdles in creating stable, large-pore COFs.

Purpose of the Study:

• To develop isoreticular series of large-pore imine COFs with pore sizes up to 5.8 nm.
• To correlate interlayer interactions with COF structure and thermal behavior.
• To investigate the role of methoxy groups in controlling pore size and stability.

Main Methods:

• Synthesis of two isoreticular series of imine COFs.
• Incorporation of methoxy groups to direct interlayer interactions and stacking modes.
• Analysis of structure-property relationships, including thermal stability and pore size.

Main Results:

• Achieved large-pore COFs with effective pore sizes up to 5.8 nm.
• Demonstrated that methoxy groups act as pore-directing anchors, influencing stacking polytypes and pore sizes.
• Found a strong correlation between stacking energy, structural integrity under thermal stress, and a novel thermally induced phase transition.

Conclusions:

• Methoxy group incorporation offers a viable strategy for enhanced structural control and stability in large-pore COFs.
• Understanding and manipulating interlayer interactions are key to designing robust, large-pore COF materials.
• The discovered thermally induced phase transition provides new insights for COF material design.