This study investigates the promotion of ZnZrOₓ catalysts for the hydrogenation of CO₂ to methanol using a variety of hydrogenation metals (Re, Co, Au, Ni, Rh, Ag, Ir, Ru, Pt, Pd, and Cu) at a low metal content of 0.5 mol%. Among these, copper (Cu) is identified as the most effective promoter, doubling the methanol productivity compared to the unpromoted catalyst. Operando X-ray absorption, infrared, and electron paramagnetic resonance spectroscopic analyses, along with density functional theory (DFT) simulations, reveal that Cu forms Zn-rich low-nuclearity CuZn clusters on the ZrO₂ surface, which correlate with the generation of oxygen vacancies. These clusters promote the rapid hydrogenation of formate into methanol while suppressing CO production. The study highlights the potential of low-nuclearity metal ensembles in CO₂-based methanol synthesis, offering an earth-abundant and cost-effective alternative to palladium promotion.This study investigates the promotion of ZnZrOₓ catalysts for the hydrogenation of CO₂ to methanol using a variety of hydrogenation metals (Re, Co, Au, Ni, Rh, Ag, Ir, Ru, Pt, Pd, and Cu) at a low metal content of 0.5 mol%. Among these, copper (Cu) is identified as the most effective promoter, doubling the methanol productivity compared to the unpromoted catalyst. Operando X-ray absorption, infrared, and electron paramagnetic resonance spectroscopic analyses, along with density functional theory (DFT) simulations, reveal that Cu forms Zn-rich low-nuclearity CuZn clusters on the ZrO₂ surface, which correlate with the generation of oxygen vacancies. These clusters promote the rapid hydrogenation of formate into methanol while suppressing CO production. The study highlights the potential of low-nuclearity metal ensembles in CO₂-based methanol synthesis, offering an earth-abundant and cost-effective alternative to palladium promotion.