Tensile-Strained 2D Bi₂Ti₂O₇ for CO₂ Photoconversion

Although the photocatalytic reduction of CO₂ to value-added chemicals, such as CO, offers a sustainable path to carbon neutrality, the optimization of the charge separation and active site density remains challenging in conventional bulk photocatalysts. In this study, it is shown that atomically thin tensile-strained 2D layered Bi₂Ti₂O₇ nanosheets (t-BT) possess high efficiency for CO₂-to-CO photoreduction. The tensile-strain-induced asymmetric Bi-O_vac-Ti sites enhance the directional charge-transfer pathway, concentrating photogenerated electrons at metallic active sites to achieve a charge separation efficiency of 91.5%. Additionally, these asymmetric sites laterally adsorb CO₂ molecules, generating an electron "push-pull" effect distinct from that of traditional Lewis acid-base pairs, to synergistically optimize ^*COOH activation and ^*C─O bond cleavage, thereby accelerating CO₂ conversion and CO desorption. Notably, t-BT produces CO at 31.06 µmol g^-1 h^-1, with ≈100% selectivity, outperforming the CO production rate of the unstrained bulk material (0.9 µmol g^-1 h^-1). This study highlights strain engineering in 2D pyrochlore architectures, revealing how defect-strain synergy overcomes conventional tradeoffs in photocatalyst design and promotes efficient CO₂-to-CO conversion.