In recent years, a technology called "artificial photosynthesis" has been developed all over the world to convert CO2 into a reducing resource by using a metal complex or a semiconductor as a photocatalyst.If it is put into practical use, CO2, which is the main cause of global warming, can be converted into useful carbon resources by using sunlight as an energy source.Complexes and inorganic semiconductors containing precious metals such as ruthenium and rhenium and rare metals have been used as photocatalysts exhibiting high activity.However, since the amount of CO2 is enormous, it was necessary to construct a new photocatalyst using only easily available elements.

　The research group found that CO2 can be highly efficiently reduced to CO when carbon nitride (an organic semiconductor consisting of carbon and nitrogen) is combined with an iron complex to form a photocatalyst.In this photocatalytic reaction, carbon nitride absorbs visible light and drives the transfer of electrons from the reducing agent to the catalyst iron complex.Using the electrons, the iron complex reduces CO2 to CO.The various values ​​used as indicators of performance were almost the same as when noble metals and rare metal complexes were used, and were more than 10 times higher than those using photocatalysts using base metals and organic molecules.

　From this research, it was demonstrated for the first time that CO2 reduction resource conversion using sunlight as an energy source can be achieved with high efficiency even if a large amount of materials such as carbon, nitrogen, and iron that exist on the earth are used.In the future, it will be a challenge to further improve the function as a photocatalyst and to achieve fusion with an oxidation photocatalyst that exists in a large amount on the earth and can use inexpensive water as a reducing agent.

Paper information:[Journal of the American Chemical Society] A carbon nitride / Fe quaterpyridine catalytic system for photo-stimulated CO2-to-CO conversion with visible light