Rapid, Ordered Polymerization of Crystalline Semiconducting Covalent Triazine Frameworks

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Crystalline porous polymers, such as covalent triazine frameworks (CTFs), are crucial for advanced applications.
• Rapid synthesis and understanding of polymerization mechanisms for crystalline CTFs are lacking.
• Existing methods do not provide scalable or rapid routes to highly crystalline CTFs.

Purpose of the Study:

• To develop a scalable and rapid synthetic strategy for crystalline and semiconducting CTFs.
• To elucidate the polymerization mechanism of crystalline CTFs.
• To enhance the photocatalytic performance of CTFs through controlled crystallinity and exfoliation.

Main Methods:

• Microwave-assisted synthesis for rapid CTF preparation (under 20 minutes).
• In situ imaging and time-dependent characterization to study polymerization.
• Ball-milling exfoliation of bulk CTFs to obtain 2D nanosheets.
• Photocatalytic hydrogen evolution rate measurements.

Main Results:

• Successfully synthesized highly crystalline and semiconducting CTFs rapidly and scalably.
• Proposed an ordered 2D polymerization mechanism involving rapid monomer polymerization into 2D sheets.
• Demonstrated that larger crystalline domains significantly improve photocatalytic performance.
• Achieved a fivefold increase in photocatalytic hydrogen evolution rate (7971 μmol g⁻¹ h⁻¹) using exfoliated 2D CTF nanosheets.

Conclusions:

• The developed microwave-assisted method offers a rapid and scalable route to crystalline CTFs.
• The proposed 2D polymerization mechanism provides fundamental insights into CTF formation.
• Optimizing crystallinity and creating 2D nanosheets are effective strategies for enhancing photocatalytic activity, particularly for hydrogen evolution.