Metal-Free Semiconductor-Based Bio-Nano Hybrids for Sustainable CO₂ -to-CH₄ 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 (CN_x ) decorated with cyanamide (NCN) groups and Methanosarcina barkeri (M. b). The self-assembled M. b-^NCN CN_x 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 ^NCN CN_x , 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.