Electron-Rich Macrocycle-Based Metal-Organic Frameworks for Efficient Photocatalytic CO₂ Reduction

Area of Science:

• Materials Science
• Chemistry
• Catalysis

Background:

• Metal-organic frameworks (MOFs) offer structural diversity and tunable electronic properties.
• Electron-donating ligands in MOFs enhance ligand-to-metal charge transfer (LMCT) for efficient charge migration.
• Optimizing ligand design is crucial for improving MOF performance in applications like photocatalysis.

Purpose of the Study:

• To synthesize and characterize novel electron-rich macrocyclic ligands and their cobalt-coordinated MOFs.
• To investigate the impact of ligand electron-donating ability on MOF photoresponse and charge transport.
• To evaluate the CO2 photoreduction performance of the developed MOFs.

Main Methods:

• Development of phenothiazine- and phenoxazine-functionalized calix[3]arene ligands.
• Coordination of ligands with cobalt to form MOFs.
• Characterization of MOF structure and electronic properties.
• Photocatalytic evaluation of CO2 reduction efficiency and selectivity.

Main Results:

• Two electron-rich macrocyclic ligands and their cobalt MOFs were successfully synthesized.
• The MOF using the phenothiazine ligand (Co-C[3]PTZ-MOF) showed superior photoresponse and charge transport.
• Co-C[3]PTZ-MOF achieved a high CO2 photoreduction efficiency of 17,800 μmol g⁻¹ h⁻¹ with 81% CO selectivity.
• Enhanced LMCT processes due to electron-rich ligands were confirmed as the origin of high performance.

Conclusions:

• Electron-rich calix[3]arene-based ligands significantly boost MOF photocatalytic activity.
• Rational ligand design is a viable strategy for developing high-performance MOF photocatalysts.
• The developed MOFs show promise for efficient CO2 photoreduction applications.