Self-sensitized Cu(ii)-complex catalyzed solar driven CO₂ reduction

Area of Science:

• Catalysis
• Photochemistry
• Materials Science

Background:

• Developing efficient catalysts from earth-abundant elements is vital for CO2 transformation and clean energy.
• Traditional methods often require external photosensitizers, increasing complexity and cost.
• Integrated solutions for light harvesting and electron transfer are needed for improved photocatalytic efficiency.

Purpose of the Study:

• To design and synthesize a self-sensitized catalyst for CO2 reduction.
• To investigate the photocatalytic mechanism of the new copper complex.
• To demonstrate the catalyst's efficiency and selectivity in converting CO2 to CO.

Main Methods:

• Synthesis of a novel Cu(II) complex, K[CuNDPA], with a dipyrrin amide ligand (NDPA).
• Photocatalytic reduction of CO2 to CO using the synthesized complex in an acetonitrile:water mixture.
• Spectroscopic investigations including EPR, UV-vis, and spectroelectrochemistry to elucidate the mechanism.
• Radical trapping experiments to probe intermediate species.

Main Results:

• The Cu(II) complex K[CuNDPA] acts as a self-sensitized photocatalyst for CO2 reduction to CO.
• Achieved a high turnover number (TON) of 1132 and turnover frequency (TOF) of 566 h⁻¹, with 99% selectivity for CO.
• Demonstrated hemilability of the ligand in the presence of water, facilitating proton relay and stabilizing a Cu(I)-NDPA intermediate.
• Spectroscopic and trapping studies supported a mechanism involving a single electron-reduced Cu(I) species and CO2 binding.

Conclusions:

• A novel, earth-abundant Cu(II) complex functions as an efficient self-sensitized photocatalyst for CO2 conversion.
• The catalyst's design integrates light harvesting and electron transfer capabilities, eliminating the need for external photosensitizers.
• This work presents a promising strategy for developing robust molecular catalysts for sustainable energy applications and environmental remediation.