Metal‐Free Semiconductor‐Based Bio‐Nano Hybrids for Sustainable CO ₂ ‐to‐CH ₄ Conversion with High Quantum Yield

Bio-nano hybrids with methanogens and nano-semiconductors provide an innovative strategy for solar-driven CO2-to-CH4 conversion; however, the efficiency mismatch between electron production and utilisation results in low quantum yield and CH4 selectivity. Herein, we report the integration of metal-free polymeric carbon nitrides (CNx) decorated with cyanamide (NCN) groups and Methanosarcina barkeri (M. b). The self-assembled M. b-NCNCNx exhibited a quantum yield of 50.3 % with 92.3 % CH4 selectivity under illumination, which outperforms other reported bio-nano hybrid systems and photocatalytic systems for CO2 reduction. This excellent performance was attributed to the distinct capacitance and conductive effects of NCNCNx, which promoted electron storage and redistribution at the biotic–abiotic interface to alleviate recombination losses and side reaction. This study provides new design guidelines for bio-nano hybrids for the sustainable photocatalytic reduction of CO2 into fuels.