Abstract: CO₂ hydrogenation to methanol is a promising route for in-situ utilization of Martian atmospheric carbon dioxide, yet conventional oxide-supported Cu catalysts usually contain non-uniform active sites and poorly controlled local structures, which can lead to CO by-product formation and limited methanol productivity. In this work, a hydroxyl-rich metal-organic framework, MOF-808, was employed as a structurally defined support. Alkali metals（M = Na, K, Cs） were first introduced through deprotonation, and Cu species were subsequently incorporated with the assistance of the alkali-metal sites, affording a series of dual-site MOF-808-MCu catalysts. The optimized catalysts, especially MOF-808-NaCu, showed markedly enhanced CO₂ hydrogenation performance, delivering a methanol space-time yield of 245 g·kgcat^–1·h^–1, much higher than that of alkali-free MOF-808-Cu（22 g·kgcat^–1·h^–1）. Characterization and theoretical calculations indicate that the alkali promoters strengthen CO₂ adsorption and activation near Cu sites, thereby favoring methanol formation and suppressing CO generation. These findings clarify the promoting role of neighboring alkali-metal sites in dual-site catalysis and offer a material-design strategy for efficient CO₂ conversion toward future Mars exploration applications.