Last week I saw a neat paper from Siti Nurhanna Riduan and her co-workers at Singapore’s Institute of Bioengineering and Nanotechnology. Ms. Riduan managed to reduce CO2 to a silylmethoxide (and, after aqueous work-up, methanol), at room temperature and moderate pressures, with an inexpensive, non-metallic catalyst. The catalyst was a carbene, meaning an organic molecule containing a carbon atom with two nonbonding electrons. The reducing agent was a hydrosilane. This relatively exotic critter provides hydrogen equivalents in a solvent-miscible, liquid form.
The reaction even worked using dry air as the source of carbon dioxide! The carbene catalyst is way cheaper than exotic metals like ruthenium usually used for this reaction, which bodes well for future applications of this reaction. To be viable at really large scales, the reaction must be adapted to a different reducing agent, or else someone will have to engineer and demonstrate an effective, energy-efficient cycle for regenerating the hydrosilane.