Hexanuclear ring cobalt complex for photochemical CO2 to CO conversion

Abstract

Photosynthesis in nature has been deemed as the most significant biochemical reaction, which maintains a relatively stable content of O2 and CO2 in the atmosphere. Herein, for a deeper comprehension of natural photosynthesis, an artificial photosynthesis model reaction of photochemical CO2 to CO conversion (CO2 +2 H+ + 2e− → CO + H2O) catalyzed by a homogeneous hexanuclear ring cobalt complex {K2[CoO3PCH2N(CH2CO2)2]}6 (Co6 complex) is developed. Using the [Ru(bpy)3]2+ as a photosensitizer and TEOA as a sacrificial electron donor, an optimal turnover frequency of 503.3 h−1 and an apparent quantum efficiency of 0.81% are obtained. The good photocatalytic CO2 reduction performance is attributed to the efficient electron transfer between Co6 complex and [Ru(bpy)3]2+, which boosts the photogenerated carriers separation of the photosensitizer. It is confirmed by the j-V curves, light-assisted UV-vis curves, steady-state photoluminescence spectra and real-time laser flash photolysis experiments. In addition, the proposed catalytic mechanism for CO2 reduction reaction catalyzed by the Co6 complex is explored by the potassium thiocyanate poison experiment, Pourbaix diagram and density functional theory calculations.