The synergistic Cu–metal oxide (Cu–MO_x) interface is critical for selective CO₂ hydrogenation to methanol, yet its mechanistic function, the central, long-debated feature of industrial Cu/ZnO/Al₂O₃, remains ambiguous. Using operando transient DRIFTS-SSITKA, we elucidate the roles of M⁺ sites (Zn²⁺, Ga³⁺, and In³⁺) on model Cu─M/SiO₂ catalysts prepared by surface organometallic chemistry (SOMC). X-ray absorption spectroscopy reveals that these promoters restructure from alloys after reduction to cationic species at the interface under reaction conditions. We find the promoter's electronic effect on formate bond strengths provides quantitative descriptors for both activity and selectivity. All catalysts follow a common formate spillover mechanism, with methoxy hydrogenation/desorption as the rate-limiting step. The intrinsic CH₃OH formation rate follows a Sabatier-type volcano with C─O bond strength, while selectivity correlates linearly with C─H bond strength (a proxy for the formate decomposition barrier). Cu─Ga/SiO₂ shows the fastest spillover, suppressing CO formation and yielding the highest selectivity; Cu─Zn/SiO₂ has optimal binding for the highest activity; In³⁺ binds formate too strongly, creating a kinetic trap on the strong-binding side of the volcano. These findings bring mechanistic clarity to the debated Cu─Zn(O) synergy, showing selectivity is governed by a balance of electronic stabilization and spillover dynamics.

The direct conversion of CO₂to CH₃OH represents an appealing strategy for the mitigation of anthropogenic CO₂emissions. Here, we report that small, narrowly distributed alloyed PdGa nanoparticles, prepared via surface organometallic chemistry from silica-supported Ga^IIIisolated sites, selectively catalyze the hydrogenation of CO₂to CH₃OH. At 230 °C and 25 bar, high activity (22.3 mol_MeOHmol_Pd^-1h^-1) and selectivity for CH₃OH/DME (81%) are observed, while the corresponding silica-supported Pd nanoparticles show low activity and selectivity. X-ray absorption spectroscopy (XAS), IR, NMR, and scanning transmission electron microscopy-energy-dispersive X-ray provide evidence for alloying in the as-synthesized material. In situ XAS reveals that there is a dynamic dealloying/realloying process, through Ga redox, while operando diffuse reflectance infrared Fourier transform spectroscopy demonstrates that, while both methoxy and formate species are observed in reaction conditions, the relative concentrations are inversely proportional, as the chemical potential of the gas phase is modulated. High CH₃OH selectivities, across a broad range of conversions, are observed, showing that CO formation is suppressed for this catalyst, in contrast to reported Pd catalysts.