Light-Driven CO 2 Reduction with a Surface-Displayed Enzyme Cascade-C 3 N 4 Hybrid.

Efficient and cost-effective conversion of CO 2 to biomass holds the potential to address the climate crisis. Light-driven CO 2 conversion can be realized by combining inorganic semiconductors with enzymes or cells. However, designing enzyme cascades for converting CO 2 to multicarbon compounds is challenging, and inorganic semiconductors often possess cytotoxicity. Therefore, there is a critical need for a straightforward semiconductor biohybrid system for CO 2 conversion. Here, we used a visible-light-responsive and biocompatible C 3 N 4 porous nanosheet, decorated with formate dehydrogenase, formaldehyde dehydrogenase, and alcohol dehydrogenase to establish an enzyme-photocoupled catalytic system, which showed a remarkable CO 2 -to-methanol conversion efficiency with an apparent quantum efficiency of 2.48% in the absence of externally added electron mediator. To further enable the in situ transformation of methanol into biomass, the enzymes were displayed on the surface of Komagataella phaffii , which was further coupled with C 3 N 4 to create an organic semiconductor-enzyme-cell hybrid system. Methanol was produced through enzyme-photocoupled CO 2 reduction, achieving a rate of 4.07 mg/(L·h), comparable with reported rates from photocatalytic systems employing mediators or photoelectrochemical cells. The produced methanol can subsequently be transported into the cell and converted into biomass. This work presents a sustainable, environmentally friendly, and cost-effective enzyme-photocoupled biocatalytic system for efficient solar-driven conversion of CO 2 within a microbial cell.