Sulfur-doping-engineered compressive strain promotes interlayer charge transport for efficient CO2 photoreduction in bismuth oxyhalides

S-substitution induces compressive strain to reduce BiOX interlayer spacing. • Reduced interlayer distance builds rapid vertical pathways for charge transport. • S-doping upshifts Bi p-band center to promote CO 2 adsorption and *COOH formation. • S-BiOBr drives efficient CO 2 photoreduction with remarkable CO evolution rates. Solar-driven CO 2 photoreduction offers a compelling route to carbon neutrality, but its efficiency is limited by sluggish charge separation and a high CO 2 activation barrier. Conventional strategies like heterojunction construction and point-defect engineering are often hampered by the trade-off between bulk charge transport and surface reaction kinetics, or by lattice instability. Herein, we overcome these kinetic bottlenecks through a doping-driven interlayer strain engineering strategy that induces long-range ordered lattice distortion in two-dimensional bismuth oxyhalides (BiOX, X=Cl, Br, I). Controlled sulfur substitution at oxygen sites introduces localized compressive strain along the [0 0 1] direction, which reduces the van der Waals interlayer spacing. This structural modulation leads to a 4.69-fold amplification of the built-in electric field, establishing a rapid vertical charge-transport pathway that accelerates carrier separation. Concurrently, the compressive strain shifts the p-band center of Bi sites upward, strengthening Bi-6p/CO 2 -2π* orbital hybridization and thereby promoting CO 2 chemisorption and activation. The synergy between accelerated charge dynamics and optimized surface electronic structure lowers the barrier for *COOH formation, enabling highly selective CO production. As a result, the optimized S-doped BiOBr catalyst achieves a CO evolution rate of 81.34 μmol g −1 ·h −1 without sacrificial agents, representing a 9.53-fold enhancement over pristine BiOBr and surpassing other BiOX variants. This work validates interlayer strain engineering as a general strategy to unlock the catalytic potential of layered materials for efficient CO 2 conversion. We developed a doping-driven strain engineering strategy that enables precise and controllable compression of the interlayer spacing in layered photocatalysts. This compression facilitates the interlayer migration of photogenerated charge carriers, thereby significantly improving photocatalytic CO 2 reduction performance. Download: Download high-res image (205KB) Download: Download full-size image