The combination of solar energy and natural hydrothermal systems will innovate the chemistry of CO₂ hydrogenation; however, the approach remains challenging due to the lack of robust and cost-effective catalytic system. Here, Zn which can be recycled with solar energy-induced approach was chosen as the reductant and Co as catalyst to achieve robust hydrothermal CO₂ methanation. Nanosheets of honeycomb ZnO were grown in situ on the Co surface, resulting in a new motif (Co@ZnO catalyst) that inhibits Co deactivation through ZnO-assisted CoO_x reduction. The stabilized Co and interaction between Co and ZnO functioned collaboratively toward the full conversion of CO₂–CH₄. In situ hydrothermal infrared spectroscopy confirmed the formation of formic acid as an intermediate, thereby avoiding CO formation and unwanted side reaction pathways. This study presents a straightforward one-step process for both highly efficient CO₂ conversion and catalyst synthesis, paving the way for solar-driven CO₂ methanation.