Abstract: The production of high-value-added chemicals using CO2-derived bioethanol as a feedstock is a key approach to achieving the circular utilisation of renewable carbon resources. As a key monomer for synthetic rubber and polymeric materials, butadienes traditional production routes rely heavily on petroleum cracking by-products; this not only creates a dependence on fossil resources but also gives rise to significant carbon emissions. The catalytic conversion of bioethanol to butadiene offers an ideal pathway for green chemistry; however, it currently faces bottlenecks such as low product yields and poor catalyst stability. Addressing key scientific questions regarding the mechanism by which bimetallic synergy influences acid and base active sites in the reaction pathway, as well as the structure–property relationship with the support, this study employed the impregnation method to prepare a series of bimetallic catalysts and systematically evaluated their performance in the ethanol-to-butadiene reaction. Taking the Zn-Zr/SiO2 catalyst—which exhibited the best performance—as the subject of study, the effects of the Zn/Zr molar ratio, total metal loading and reaction conditions were further investigated. The structure–property relationships were analysed using techniques such as XRD, SEM, EDS, BET, FTIR, XPS and CO2/NH3-TPD. The results indicate that at a Zn/Zr molar ratio of 2:5, a total metal loading of 11.5 per cent, a reaction temperature of 375℃ and a space velocity of 0.97 h-1, the ethanol conversion reached 96.2 per cent, the butadiene selectivity was 49.8 per cent, and the space-time yield was 0.27 g·g-1·h-1, whilst maintaining good stability during 50 hours of continuous reaction. Characterisation results revealed that Zn and Zr species are highly dispersed on the surface of the SiO2 support, creating a suitable mesoporous structure and distribution of acid and base sites. Specifically, Zn promotes ethanol dehydrogenation and modulates basic sites, whilst Zr drives the condensation of acetaldehyde via Lewis acid sites. The two elements work synergistically to facilitate the orderly progression of the main reaction and suppress side reactions, thereby significantly enhancing butadiene yield and catalyst stability. These findings elucidate the nature of bimetallic synergistic catalysis and clarify how the surface structure and acid–base properties of the support regulate reaction pathways, thereby providing a theoretical basis for the design of highly efficient catalysts for the production of butadiene from ethanol and for the high-value utilisation of renewable carbon resources.