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

Abstract Solar‐driven selective synthesis of C 2 chemicals from CO 2 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 Bi 1 ─O─Bi 2 site at the Bi 3 NbO 7 nano‐dots/Bi 3 O 4 Br nanosheet (BNO/BOB) interface to promote C─C coupling for acetic acid production, the photocatalytic conversion rate of CO 2 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 Bi 1 ─O─Bi 2 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.