Enhancing CO2 photoreduction via the perfluorination of Co(II) phthalocyanine catalysts in a noble-metal-free system

Abstract

The manufacture of high-performance photocatalytic systems based on earth-abundant elements remains a key challenge, urging operative strategies for catalyst design. Herein, we present the construction of an efficient and noble-metal-free molecular system for the photoreduction of CO2 to CO using a Cu(I) photosensitizer and Co(II) phthalocyanine catalysts. It was found that the perfluorination of Co(II) phthalocyanine shows enhanced catalytic performance for CO2-to-CO conversion compared with pristine Co(II) phthalocyanines, achieving a remarkable apparent quantum yield of 58.2% at 425 nm, which is three times that of the pristine one (19.0%). The Cu(I)/Co(II) system also achieved a maximum turnover number of 9185 and near-unity selectivity. These improvements can be attributed to the electron-withdrawing effect of the fluorine substituents, which lowers the catalytic overpotential for catalysis and decreases the Gibbs free energy of the rate-determining Co-carboxylate-forming step. This work indicates that perfluorination is an effective approach to optimize the catalytic performance of molecular catalysts.