Sodium-induced solid-phase hydrogenation of carbon dioxide to formate by mechanochemistry

Transforming carbon dioxide (CO) into value-added fuels is an innovative way to address both the energy and the climate issues. In particular, formic acid, as formate salt, is recently attracting attention because this acid can be used as a chemical fuel in fuel cells. Here we present a novel method for hydrogenating CO-containing industrially relevant salts, such as sodium bicarbonate ammonium bicarbonate and ammonium carbonate, to formate. Metal sodium (Na) was used as the reducing agent to break the C–O bond and as a inducer of hydrogen transfer. A ball-milling mechanochemical method was used for the solid-phase reaction. Results show that reducing (NH)CO(s) with sodium yielded 41.4% formate after 7 h under catalyst-free conditions. Our new method has thus promising potential applications in the emerging CO economy.