The production of multi-carbon compounds through CO2 photoreduction (CO2PR) holds great promise but faces challenges due to high kinetic barriers and the sluggish process of C-C coupling. Overcoming these obstacles requires fine engineering of active sites. In this study, Ni active sites are engineered through the synergistic effect of metal-oxo cluster (Mo7O246−) and hydroxyl vacancy (VOH). In contrast to the Ni sites unmodified with Mo7O246− and VOH, which are unable to produce multi-carbon products, the constructed electron-enriched Ni active sites exhibit an impressive selectivity of up to 43.02% and a high yield rate of 246.70 µmol g−1 h−1 for C2H6, which represent one of the best results for CO2PR to C2H6. Through a comprehensive investigation involving operando experiments and theoretical simulations, hydroxyl vacancy and the formed Mo─O─Ni bonds is demonstrated due to the filling of hydroxyl vacancies with oxygen atoms from Mo7O246− synergistically constructed electron-rich Ni sites. Such Ni sites efficiently catalyze CO2 conversion to C2H6 by enhancing the adsorption of *CO, promoting subsequent hydrogenation, and enabling low energy barriers for CO2 hydrogenation to *OCOH and the coupling of *CH3 intermediates. This study provides deeper insights into the photocatalytic process, highlighting the significance of tailored active sites for efficient CO2 conversion.