Post-Synthetically Cluster-Metalated Hf-MOF for Aqueous Photocatalytic CO2 Reduction to Methanol

Area of Science:

• Heterogeneous catalysis
• Materials science
• Photochemistry

Background:

• Single-site heterogeneous catalysis offers precise control over catalytic processes.
• Metal-organic frameworks (MOFs) provide tunable platforms for catalyst design.
• Efficient CO2 conversion is crucial for sustainable energy solutions.

Purpose of the Study:

• To develop an integrated photocatalytic system for selective CO2 reduction.
• To investigate the structure-activity relationship in a postmodified MOF catalyst.
• To explore the mechanism of visible-light-driven CO2-to-methanol conversion.

Main Methods:

• Postsynthetic modification of Hf-MOF-808 with Ni(II) sites and a Ru-based photosensitizer.
• Characterization using X-ray absorption spectroscopy (XAS).
• Photocatalytic CO2 reduction experiments under visible light irradiation.
• Spectroscopic studies (FSTA, in situ DRIFT) and DFT calculations to elucidate the reaction mechanism.

Main Results:

• The Hf-Ni-MBA-Ru-MOF catalyst achieved selective CO2 reduction to methanol with a yield of 404 μmol·g⁻¹ in 10 hours.
• The integrated system demonstrated high selectivity and production rates in aqueous media.
• Femtosecond transient absorption spectroscopy and DFT calculations confirmed excited-state electron transfer from the photosensitizer to the Ni(II) catalytic sites.
• In situ DRIFT spectroscopy identified reaction intermediates.

Conclusions:

• The developed Hf-Ni-MBA-Ru-MOF is a highly effective single-site photocatalyst for sustainable CO2 conversion to methanol.
• Confinement within the MOF enhances photosensitizer lifetime and catalytic efficiency.
• The study provides mechanistic insights into the photocatalytic CO2 reduction process.