Photosynthetic Fixation of CO₂ in Alkenes by Heterogeneous Photoredox Catalysis with Visible Light

Light-driven fixation of CO₂ in organics has emerged as an appealing alternative for the synthesis of value-added fine chemicals. Challenges remain in the transformation of CO₂ as well as product selectivity due to its thermodynamic stability and kinetic inertness. Here we develop a boron carbonitride (BCN) with the abundant terminal B/N defects around the mesoporous walls, which essentially enhances surface active sites as well as charge transfer kinetics, boosting the overall rate of CO₂ adsorption and activation. In this protocol, anti-Markovnikov hydrocarboxylation of alkenes with CO₂ to an extended carbon chain is achieved with good functional group tolerance and specific regioselectivity under visible-light irradiation. The mechanistic studies demonstrate the formation of CO₂ radical anion intermediate on defective boron carbonitride, leading to the anti-Markovnikov carboxylation. Gram-scale reaction, late-stage carboxylation of natural products and synthesis of anti-diabetic GPR40 agonists reveal the utility of this method. This study sheds new insight on the design and application of metal-free semiconductors for the conversion of CO₂ in an atom-economic and sustainable manner.