Molecular engineering of conjugated polyelectrolyte-enzyme biohybrid sheets for solar CO2 conversion

Bridging synthetic light-harvesting materials with enzymatic CO 2 fixation enables semi-artificial photosynthesis, but molecular design principles governing semiconductor-biocatalyst interfaces remain underdeveloped. Here, we establish a modular molecular design framework using conjugated polyelectrolytes (CPEs) as solution-processable, metal-free photosensitizers to construct photocatalytic biohybrid sheets through the spontaneous surface adsorption of formate dehydrogenase (FDH). Systematic variation of side-chain functionality and conjugated backbone structure reveals structure-property-activity relationships that dictate direct electron transfer at the abiotic-biotic interface. Molecular control over surface charge density, hydration environment, and long-range charge separation enhances CO 2 -to-formate reduction rates by more than two orders of magnitude. The optimized biohybrid sheet achieves a benchmark turnover frequency of 27,500 h ‒1 with stable operation over 48 h. These findings define actionable molecular design principles for co-optimizing optoelectronic properties and biointerfacial chemistry in organic semiconductors to construct high-performance biohybrid platforms for solar chemical production.