Photocatalytic CO₂ reduction is a promising strategy for sustainable development. Optimizing the structure of photocatalysts to facilitate the separation of electron–hole pairs for improved performance is not only highly desirable but also challenging. Aiming to improve the photocatalytic reduction of CO₂, Ru is selected and applied to modify Bi₂MoO₆. Compared to pure Bi₂MoO₆, Ru-Bi₂MoO₆ exhibits substantially excellent photocatalytic activity in CO₂ reduction with CO generation of 142.77 μmol⁻¹g⁻¹ and selectivity of 100% under simulated sunlight. The enhancement might be attributed to the following: 1) Ru⁰ acting as an electron acceptor facilitates unique interaction and activation with CO, 2) Ru⁴⁺ doping enhances light absorption with addition impure energy levels within the bandgap, 3) ultrathin layers is in favor of improving the specific surface area and providing more exposed sites for CO₂ adsorption and activation, and 4) interfaces between Ru and Bi₂MoO₆ accelerate charge transfer and separation, and electrons and holes are efficiently transferred to Ru and Ru⁴⁺, respectively, facilitating the reduction and oxidation reactions. This work provides a new approach to improve photocatalytic CO₂ abatement and further presents valuable new insights into the design modification of photocatalytic systems.