Transforming atmospheric CO2 into alternative fuels: a metal-free approach under ambient conditions

Abstract

This work demonstrates the first-ever completely metal-free approach to the capture of CO₂ 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 CO₂ capture (aNHC-H, HCOO, B(OH)₃) was structurally characterized by single-crystal X-ray diffraction. Interestingly, the captured CO₂ can be released by heating the intermediate, or by passing this compound through an ion-exchange resin. The capture of CO₂ from air can even proceed in the solid state via the formation of a bicarbonate complex (aNHC-H, HCO₃, 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.