Twisted Stacking 2D Covalent Organic Frameworks with Directional Electron Transport for Boosting CO₂ Photoreduction

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Conventional 2D covalent organic frameworks (COFs) suffer from inefficient electron transfer, limiting their application in photocatalytic CO2 reduction.
• Random in-plane diffusion of photogenerated electrons in slip-stacked COFs hinders performance.
• Moiré superlattices offer inspiration for regulating interlayer interactions through rotational stacking.

Purpose of the Study:

• To introduce a coordination-directed interlayer twisting strategy for constructing novel covalent organic frameworks (TSCOFs).
• To enhance photocatalytic CO2 reduction efficiency by optimizing electron transfer pathways.
• To establish a generalizable design principle for high-performance CO2 photoreduction materials.

Main Methods:

• Coordination-directed interlayer twisting strategy utilizing Ru-bpy moieties as molecular pivots.
• Structural analyses and theoretical calculations to elucidate energy-level alignment and electron transfer mechanisms.
• Femtosecond transient absorption spectroscopy (fs-TAS) to investigate ultrafast charge dynamics.

Main Results:

• Construction of twisted stacking TSCOFs with an interlayer rotation of approximately 55.3°.
• Demonstrated stepwise energy-level alignment facilitating directional electron transfer from COF skeleton to metal centers.
• Achieved a CO production rate of 118.5 μmol g⁻¹ h⁻¹ for TSCOF-2, a 3-4 fold enhancement over parallel-stacked analogues.

Conclusions:

• Molecular-level interlayer twisting effectively modulates charge migration in COFs.
• TSCOFs exhibit significantly enhanced photocatalytic CO2 reduction activity due to improved charge transport.
• This strategy provides a viable pathway for designing advanced photocatalysts for CO2 conversion.