Carbon dioxide reduction to methane and coupling with acetylene to form propylene catalyzed by remodeled nitrogenase

A doubly substituted form of the nitrogenase MoFe protein (α-70 ⱽᵃˡ→ᴬˡᵃ, α-195 ᴴⁱˢ→ᴳˡⁿ) has the capacity to catalyze the reduction of carbon dioxide (CO ₂) to yield methane (CH ₄). Under optimized conditions, 1 nmol of the substituted MoFe protein catalyzes the formation of 21 nmol of CH ₄ within 20 min. The catalytic rate depends on the partial pressure of CO ₂ (or concentration of HCO ₃⁻) and the electron flux through nitrogenase. The doubly substituted MoFe protein also has the capacity to catalyze the unprecedented formation of propylene (H ₂C = CH-CH ₃) through the reductive coupling of CO ₂ and acetylene (HC≡CH). In light of these observations, we suggest that an emerging understanding of the mechanistic features of nitrogenase could be relevant to the design of synthetic catalysts for CO ₂ sequestration and formation of olefins.