Nitrogenases catalyze ATP-independent CO₂-reduction to C₁–C₄ hydrocarbons in reactions driven by chemical reductants (Eu^II–DTPA) or light (quantum dots). MoFe and VFe proteins show higher activity in H₂O and D₂O, respectively, for the Eu^II–DTPA driven CO₂-reduction to hydrocarbons. This atypical CO₂-to-fuel Fischer–Tropsch type conversion offers a platform for mechanistic studies and the potential for designing sustainable CO₂ recycling strategies.

Nitrogenase is a versatile metalloenzyme that activates and reduces small molecules like N₂, CO, and CO₂ into value-added chemicals at ambient conditions. Previously, it is shown that the Mo-nitrogenase could reduce CO₂ to CO, but not to hydrocarbons, in an ATP-dependent reaction. Here, it is reported that the ability of the catalytic component of Mo-nitrogenase (MoFe protein) enables ATP-independent reduction of CO₂ to up to C₄ hydrocarbons in room-temperature reactions driven by a chemical reductant (Eu^II–DTPA) or visible light (via CdS@ZnS (CZS) quantum dots). Moreover, an opposite deuterium isotope effect is observed on the Eu^II–DTPA driven reactions of CO₂ reduction by MoFe protein and its V-counterpart (VFe protein), in that the former displays higher activities in H₂O, and the latter displays higher activities in D₂O. These results provide an important foundation for further mechanistic exploration of the nitrogenase-enabled, atypical Fischer–Tropsch type reaction that uses CO₂ instead of CO as a substrate; moreover, they serves as a potential template for the future development of nitrogenase-based applications that effectively recycle the greenhouse gas CO₂ into valuable fuel products.