Reduction of CO2 in the presence of light via excited-state hydride transfer reaction in a NADPH-inspired derivative

Abstract

The photo-catalytic reduction of CO₂ into chemical feedstocks using solar energy has attracted vast interest in environmental science because of global warming. Based on our previous study on the CO₂ complex with one of the benzimidazoline (BI) derivatives, we explore the photochemical reduction of CO₂ in one of the benzimidazoline derivatives (1,3-dimethyl-5,6-diol-2,3-dihydro-1H-benzimidazole) by quantum-chemical methods. Our results reveal that carbon dioxide can be reduced to formate (HCOO⁻) by a hydride transfer reaction in the excited state of this complex of benzimidazoline derivative and CO₂. While the ground-state hydride transfer reaction in this complex exhibits a substantial barrier, a charge-transfer can occur in the first singlet excited state of the complex in the UV-A region (326 nm), and after overcoming a moderate barrier (∼0.4 eV) the system can have access to the products. The interaction with a polar solvent decreases further the barrier such that the reaction in dimethyl sulfoxide can proceed with a negligibly small barrier (∼0.1 eV) or in a nearly barrierless manner. Our results show that this benzimidazoline derivative may act as a catalyst in the photoreduction of CO₂.