Structural-coupling driven cobalt metalloporphyrin⊂MIL-101(Fe) hybrids for efficient photocatalytic CO₂ reduction

Area of Science:

• Materials Science
• Catalysis
• Renewable Energy

Background:

• Metal-organic frameworks (MOFs) are crucial for carbon capture and utilization (CCU) but enhancing their photocatalytic CO2 conversion efficiency remains a challenge.
• Existing MOFs often require specific conditions or sacrificial agents, limiting their practical application in solar-to-chemical energy conversion.

Purpose of the Study:

• To develop a hybrid MOF using a mixed-ligand strategy to improve photocatalytic CO2 conversion efficiency.
• To investigate the synergistic effects of incorporating a cobalt-metalated porphyrin into an amine-functionalized MOF for enhanced solar-to-chemical energy conversion.

Main Methods:

• A mixed-ligand strategy was employed to synthesize a hybrid MOF (CTN ⊂ NM) by integrating cobalt-metalated tetrakis(4-carboxyphenyl)porphyrin (CTN) into amine-functionalized MIL-101(Fe) (NM).
• The photocatalytic activity for CO2 conversion to formic acid (HCOOH) was evaluated under visible light, with and without a sacrificial electron donor.
• Characterization techniques were used to analyze the structure, light absorption, and catalytic properties of the hybrid MOF.

Main Results:

• The optimized hybrid MOF (Co/Fe molar ratio of 0.40) achieved a HCOOH production rate of 119.11 μmol g⁻¹ h⁻¹ under visible light without a sacrificial agent, a 4.2-fold increase over the pristine NM.
• With a sacrificial electron donor, the HCOOH production rate further increased to 179.87 μmol g⁻¹ h⁻¹.
• The enhanced performance is attributed to the synergistic integration of CTN and NM, which broadens light absorption, reduces charge recombination, and accelerates CO2 reduction kinetics.

Conclusions:

• The mixed-ligand hybridization approach effectively enhances the photocatalytic CO2 conversion efficiency of MOFs.
• The cobalt center in the porphyrin acts as an active site for CO2 adsorption and activation, promoting selective conversion to HCOOH.
• This study offers valuable insights for designing advanced MOF-based photocatalysts for sustainable fuel production and carbon-neutral energy solutions.