A renewable amine for photochemical reduction of CO2

Photochemical reduction of CO2 (to produce formic acid) can be seen both as a method to produce a transportable hydrogen-based fuel and also to reduce levels of CO2 in the atmosphere. However, an often overlooked necessity for photochemical CO2 reduction is the need for a sacrificial electron donor, usually a tertiary amine. Here, we describe a new strategy for coupling the photochemical reduction of CO2 to photochemical water splitting, and illustrate this with a prototype example. Instead of seeking to eliminate the use of an external reducing agent altogether, our alternative strategy makes the reducing agent recyclable. This has two potential advantages over the direct coupling of CO2 reduction and water oxidation. First, it allows the two redox reactions to be carried out with existing chemistry, and second, it permits these reactions to be conducted under mutually incompatible conditions