Interfacial electron transfer engineering in semi-artificial photosynthesis biohybrid systems for CO2 fixation

The integration of semi-artificial photosynthesis (SAP) with microbial metabolism offers a transformative approach for sustainable CO 2 fixation. However, sluggish transmembrane electron transfer remains a fundamental bottleneck that limits solar-to-chemical conversion efficiency. This study provides a comprehensive review of recent advances in interfacial electron transfer engineering in biohybrid SAP systems across extracellular, transmembrane, and intracellular regimes. First, diverse strategies to modulate the bio-abiotic interface and enhance electron flux, ranging from random mixing and surface anchoring to advanced membrane grafting and in situ biomineralization, are critically analyzed. Furthermore, metabolic partitioning states of photogenerated electrons are reviewed across various microbial classes, including Gram-positive and Gram-negative bacteria and archaea. The electron distribution during the synthesis of products ranging from C1 compounds (formate and methane) to complex C2+ molecules (acetate, isopropanol, and polyhydroxybutyrate) is discussed, and the importance of balancing the generation of redox equivalents and energy carriers is highlighted. Finally, this review proposes a roadmap for future research to achieve high-performance and industrially viable biohybrid platforms, emphasizing the synergy between materials science and metabolic engineering.