Significant　progress　has　been　evidenced　in　the　development　of　the　synergistic　effect　of　the　various　active　sites　for　selective　catalyzing　CO2　hydrogenation　toward　the　target　product.　Unveiling　the　roles　of　different　active　sites　is　conducive　to　understanding　the　structure–activity　relationship　in　complex　reactions.　In　this　study,　the　pretreatment　atmosphere　plays　a　pivotal　role　in　modulating　active　site　properties.　The　optimized　Ar-pretreated　Cu-UiO-66-Ar　catalyst　shows　a　high　methanol　space–time　yield　of　733　μmol　gcat.−1h−1　at　200　°C,　3.0　MPa,　which　is　2.7　times　than　that　of　H2-pretreated　Cu-UiO-66-H2　catalyst　(274　μmol　gcat.−1h−1).　We　revealed　the　interface　(Cu–O–Zr　sites)　and　Cu　nanoparticles　(Cu–Cu　sites)　co-play　a　pivotal　role　in　promoting　CO2　conversion　and　H2　dissociation　via　Cu–Cu　sites　feeds　H*　to　Cu–O–Zr-anchored　CO*/HCO*　species.　Rational　contrast　experiments　of　the　in-situ　DRIFTS　highlight　the　accelerated　elementary　steps　in　the　CO2　conversion　process　contact　with　the　enhanced　catalytic　activity.　Thus,　this　work　is　helpful　to　advance　the　understanding　of　the　potential　mechanism　in　a　composite　cross-reaction　network.　©　2025　Elsevier　B.V.