Boosting Light-Driven CO₂ Conversion Into CO by a Polypyridine Iron(II) Catalyst Using an Organic Sensitizer

Area of Science:

• Photocatalysis
• Green Chemistry
• Materials Science

Background:

• Direct photochemical conversion of CO₂ into single carbon products is a significant challenge in CO₂ reduction reaction (CO₂RR) catalysis.
• Developing efficient and selective noble-metal-free systems is crucial for sustainable energy solutions.

Purpose of the Study:

• To develop a novel, noble-metal-free photochemical system for efficient and selective CO₂ conversion into CO.
• To investigate the mechanism behind the system's performance and stability.

Main Methods:

• Combination of an organic photosensitizer with a heptacoordinated iron(II) complex.
• Photochemical reaction utilizing N,N-diisopropylethylamine (DIPEA) and 2,2,2-trifluoroethanol (TFE) as electron and proton donors.
• Transient absorption spectroscopy for mechanistic studies.

Main Results:

• Achieved unprecedented performances in CO₂ to CO conversion: quantum yield (Φ_CO) up to 36%, turnover number (TON_CO) >1000, and selectivity >99%.
• Demonstrated system stability due to fast electron transfer rates protecting the photosensitizer from degradation.
• Identified the crucial role of rapid electron transfer from the photogenerated reduced dye to the catalyst.

Conclusions:

• The developed system offers an efficient and selective pathway for CO₂ conversion into CO using earth-abundant elements.
• The synergistic combination of organic photosensitizers and iron complexes shows great potential for solar energy conversion into fuels.
• Fast electron transfer dynamics are key to achieving high stability and performance in photochemical CO₂ reduction.