Allosteric Modulation toward Nonionic Covalent Organic Framework Nanosheets.

Area of Science:

• Materials Science
• Nanotechnology
• Supramolecular Chemistry

Background:

• Nonionic covalent organic framework nanosheets (nCOFNs) are promising building blocks but challenging to synthesize in solution.
• Controlling both intralayer and interlayer interactions is crucial for high-quality nCOFN synthesis.
• Allostery, a biological regulation mechanism, has not been explored in synthetic materials like COFs.

Purpose of the Study:

• To introduce an allosteric modulation strategy for solution-phase synthesis of β-ketoenamine-linked nCOFNs.
• To investigate the role of secondary amines as allosteric modulators in controlling nCOFN assembly.
• To achieve high crystallinity and large aspect ratios in nCOFNs under mild conditions.

Main Methods:

• Utilized a secondary amine as an allosteric modulator to control enol-keto tautomerization and steric hindrance.
• Optimized modulator properties (N exposure, side group size) for balanced allosteric effects.
• Employed mild, ambient conditions for the synthesis of nCOFNs.

Main Results:

• Successfully synthesized high-quality nCOFNs with high crystallinity and aspect ratios >1000.
• Achieved high yields (up to 82%) under mild, ambient conditions.
• Demonstrated excellent solution processability, enabling assembly into membranes with ultrahigh methanol permeance (127 L m⁻² h⁻¹ bar⁻¹).

Conclusions:

• The allosteric modulation strategy offers a novel approach for synthesizing advanced nCOFNs.
• The synthesized nCOFNs exhibit superior performance in membrane applications, including durability and pharmaceutical purification.
• Practical application potential demonstrated through the fabrication of large-area flat-sheet and hollow fiber membranes.