Metal-free reduction of CO2 to formate using a photochemical organohydride-catalyst recycling strategy

Increasing levels of CO2 in the atmosphere is a problem that must be urgently resolved if the rise in current global temperatures is to be slowed. Chemically reducing CO2 into compounds that are useful as energy sources and carbon-based materials could be helpful in this regard. However, for the CO2 reduction reaction (CO2RR) to be operational on a global scale, the catalyst system must: use only renewable energy, be built from abundantly available elements and not require high-energy reactants. Although light is an attractive renewable energy source, most existing CO2RR methods use electricity and many of the catalysts used are based on rare heavy metals. Here we present a transition-metal-free catalyst system that uses an organohydride catalyst based on benzimidazoline for the CO2RR that can be regenerated using a carbazole photosensitizer and visible light. The system is capable of producing formate with a turnover number exceeding 8,000 and generates no other reduced products (such as H-2 and CO).

Automated summary

Increasing levels of CO2 in the atmosphere is a pressing issue that needs to be addressed urgently to mitigate global temperature rise. A catalyst system that chemically reduces CO2 into useful compounds and meets certain criteria is necessary for global scale CO2RR. We propose a transition-metal-free catalyst system using an organohydride catalyst based on benzimidazoline for CO2RR, which can be regenerated using a carbazole photosensitizer and visible light, with promising results.