Transforming atmospheric CO(2) into alternative fuels: a metal-free approach under ambient conditions

This work demonstrates the first-ever completely metal-free approach to the capture of CO(2) from air followed by reduction to methoxyborane (which produces methanol on hydrolysis) or sodium formate (which produces formic acid on hydrolysis) under ambient conditions. This was accomplished using an abnormal N-heterocyclic carbene (aNHC)–borane adduct. The intermediate involved in CO(2) capture (aNHC-H, HCOO, B(OH)(3)) was structurally characterized by single-crystal X-ray diffraction. Interestingly, the captured CO(2) can be released by heating the intermediate, or by passing this compound through an ion-exchange resin. The capture of CO(2) from air can even proceed in the solid state via the formation of a bicarbonate complex (aNHC-H, HCO(3), B(OH)(3)), which was also structurally characterized. A detailed mechanism for this process is proposed based on tandem density functional theory calculations and experiments.