Light-driven biohybrid system utilizes N₂ for photochemical CO₂ reduction

Attempting to couple photochemical CO₂ reduction with N₂ fixation is usually difficult, because the reaction conditions for these two processes are typically incompatible. Here, we report that a light-driven biohybrid system can utilize abundant, atmospheric N₂ to produce electron donors via biological nitrogen fixation, to achieve effective photochemical CO₂ reduction. This biohybrid system is constructed by incorporating molecular cobalt-based photocatalysts into N₂-fixing bacteria. It is found that N₂-fixing bacteria can convert N₂ into reductive organic nitrogen and create a localized anaerobic environment, which allows the incorporated photocatalysts to continuously perform photocatalytic CO₂ reduction under aerobic conditions. Specifically, the light-driven biohybrid system displays a high formic acid production rate of over 1.41 × 10^-14 mol h^-1 cell^-1 under visible light irradiation, and the organic nitrogen content undergoes an over-3-fold increase within 48 hours. This work offers a useful strategy for coupling CO₂ conversion with N₂ fixation under mild and environmentally benign conditions.