Effective CO₂ Photoreduction Synergistically Boosted by Built-In Electronic Field and Coplanar Covalent Triazine...

Area of Science:

• Materials Science
• Catalysis
• Photochemistry

Background:

• Photocatalytic CO2 reduction efficiency is limited by poor charge separation and carrier transport.
• Constructing planar covalent metal-organic frameworks (CMOFs) with built-in electric fields (IEF) is a promising strategy to overcome these limitations.
• Synthesizing highly planar CMOFs remains a significant challenge.

Purpose of the Study:

• To develop a facile and efficient molecular-level strategy for constructing highly planar CMOFs.
• To enhance the photocatalytic efficiency of CO2 reduction by improving charge separation and carrier transport.
• To investigate the structure-activity relationship in the synthesized CMOFs for CO2 reduction.

Main Methods:

• Synthesis of copper-based covalent triazine frameworks (CTF-Z) using planar triazine linkers and triangular copper clusters (Cu3) as monomers.
• Characterization of the CTF-Z structure, including planarity (dihedral angle) and local IEF.
• Photocatalytic CO2 reduction experiments using CTF-Z, measuring CO production rates without sacrificial agents or photosensitizers.
• Experimental and theoretical investigations to elucidate the mechanism of enhanced photocatalysis.

Main Results:

• Successfully synthesized CTF-Z with outstanding coplanarity (dihedral angle of 0.001°) and a significant local IEF.
• CTF-Z demonstrated effective photocatalytic CO2 reduction to CO with a production rate of 73.65 μmol g-1 h-1.
• The photocatalytic activity of CTF-Z was 4.5 times higher than a control material (FDM-71) with a larger dihedral angle.
• Theoretical studies indicated that the electron-withdrawing triazine ring in the D-A-D structure promotes electron participation in redox reactions and facilitates *COOH intermediate formation.

Conclusions:

• The developed CTF-Z materials exhibit excellent molecular-level design for enhanced charge carrier separation and migration.
• The high planarity and built-in electric field in CTF-Z are crucial for efficient photocatalytic CO2 reduction.
• This work provides a viable strategy for designing advanced CMOFs for energy conversion applications.