Capture to convert

Abstract

An N-heterocyclic carbene (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene; pictured) was selected for its high CO₂ binding and activation ability together with its resistance to reduction under electrocatalytic conditions. This sorbent was found to react quantitatively with dilute sources of CO₂ in the range 0.04–10%. The molecular electrocatalyst iron tetraphenylporphyrin (pictured) was able to directly reduce the carbene–CO₂ complex under applied potential in tetrahydrofuran (THF) solution. Notably, even with water as the proton source, a high selectivity towards carbon products was observed. Furthermore, the dominant product was the eight-electron reduced CH₄ (85% Faradaic efficiency), even though this Fe porphyrin catalyst typically favours the two-electron reduced CO when directly reducing CO₂ in the absence of carbene.

This report supports the idea that integrated electrochemical CO₂ capture and conversion may be an effective strategy for direct utilization of dilute CO₂ emissions. Unexpectedly, it also reveals the role that the sorbent can have as a catalytic auxiliary to alter the inherent selectivity of a given catalyst towards more unusual products.