Oxygen vacancy-enriched ultrafine tetragonal ZrO2 was introduced as a support for copper nanoparticles to enhance the energy efficiency of CO2 hydrogenation for methanol synthesis. In situ spectroscopic techniques confirmed the oxygen vacancy-mediated single-electron CO2 activation. The resulting highly efficient catalyst yielded a methanol production rate of 550 mg gcat-1 h-1 at 200 °C, outperforming state-of-the-art Cu-based catalysts.