Epitaxial Active Interface to Construct Intralattice‐Bonded Asymmetric Bi ₁ ─O─Bi ₂ Sites for Robust CO ₂ Photoreduction to Acetic Acid

Solar-driven selective synthesis of C₂ chemicals from CO₂ is a crucial pathway for carbon cycling, but it is limited by the high kinetic barrier of C─C coupling. This study proposes an epitaxial growth strategy for lattice-bonded asymmetric sites. By constructing a Bi₁─O─Bi₂ site at the Bi₃NbO₇ nano-dots/Bi₃O₄Br nanosheet (BNO/BOB) interface to promote C─C coupling for acetic acid production, the photocatalytic conversion rate of CO₂ to acetic acid can reach 192.3 µmol·g^-1·h^-1, with 91.4% selectivity. The apparent quantum efficiency at 380 and 400 nm reach 9.49% and 6.57%, respectively. The key mechanism originates from a cascade electron effect triggered by the interfacial Bi₁─O─Bi₂ sites: the interfacial charge redistribution induces a strong built-in electric field, where high-energy electrons selectively occupy the 2π antibonding orbitals of CO^* intermediates, significantly weakening the C─O bond in CO^* intermediate. Furthermore, the asymmetric charge redistribution effectively neutralizes the electrostatic repulsion between adjacent CO^* intermediates, synergistically stabilizing the OCCO^* transition state through d-π electron feedback from Bi sites. The dual effects synergistically lower the energy barriers for both the C─C coupling and hydrogenation steps, ultimately steering the reaction pathway towards long-lasting acetic acid formation.