Engineering Asymmetric Active Sites with Spin Polarization for Selective Photocatalytic CO₂-to-CH₃COOH Conversion

Selective photocatalytic reduction of CO₂ to CH₃COOH is highly desirable but hindered by poor intermediate stabilization and sluggish C-C coupling. Here we report a coordination-environment engineering strategy to construct asymmetric Co active sites and induce intrinsic spin polarization by nitrogen incorporation into Co₃O₄. Nitrogen substitution and oxygen vacancy formation generate Co sites with distinct coordination and charge distributions, stabilizing *CO intermediates and lowering the C-C coupling barrier. Concurrently, spin polarization enhances charge carrier separation, further intensified by an external magnetic field. In situ spectroscopy and theoretical calculations confirm the synergistic role of asymmetry and spin effects in facilitating intermediate formation and CH₃COOH production. The optimized N-Co₃O_4-X catalyst achieves a CH₃COOH yield of 41.4 μmol g^-1 h^-1 with 95% electron selectivity under external magnetic field. This work presents a dual-modulation strategy for efficient CO₂-to-C₂ conversion.