Cu Sites Induced Polarization Enhancement and Symbiotic Electronic Structure Regulation to Facilitate CO ₂ Photoreduction

ABSTRACT The sluggish charge transfer and weak surface‐site reactivity critically limit CO ₂ photoreduction efficiency. While the crystal structure dictates bulk charge separation, the surface atomic configuration governs reaction kinetics and thermodynamics. Thus, concurrent optimization of both domains is essential. In this work, we present a concise strategy for the selective conversion of CO ₂ to CO using polar Bi ₄ O ₅ Br ₂ nanosheets modified with Cu atoms to induce bulk polarization enhancement and symbiotic electronic structure regulation (SESR). The SESR effect establishes a dynamic coupling between internal polarization and surface electronic states. Cu incorporation into the asymmetric Bi ₄ O ₅ Br ₂ layered framework enhances intrinsic polarization through polar‐unit stacking, thereby extending carrier lifetime by 48.6‐fold and facilitating efficient charge separation and migration. Meanwhile, the strengthened polarization modulates the surface electronic configuration of Cu sites, promoting CO ₂ adsorption and activation, as supported by experimental characterization and theoretical simulation under polarized conditions. Without any sacrificial agents or sensitizers, Cu‐Bi ₄ O ₅ Br ₂ achieves a remarkable CO ₂ ‐to‐CO rate of 45.34 µmol g ⁻¹ h ⁻¹ with high selectivity in pure water. This work elucidates the cooperative interplay between polarization fields and surface electronic regulation, providing a generalizable paradigm for manipulating charge dynamics and catalytic‐site chemistry toward efficient solar‐driven CO ₂ conversion.