Domino CO ₂ -to-Methanol Hydrogenation Enabled by a Catalyst-like Gas−Water Interface via NO Microbubble-Driven Redox Radicals

The development of efficient CO2 reduction catalysts hinges on the precise control of intermediate binding strength to balance reactant adsorption and product desorption. Here, we demonstrate that NO microbubble gas−water interfaces can function as catalyst-like platforms for CO2 hydrogenation to methanol. By generating NO microbubbles in situ from acidified KNO2, we create a confined gas−water interface that triggers hydroxyl radical (•OH) and hydrated electrons (e−aq), while facilitating intermediate (CO2•−) formation. We show that lower KNO2 concentration favors redox radical formation, yet higher KNO2 concentration scavenges redox radicals thus producing NH4+ and NO3−. High-resolution mass spectroscopy and electron paramagnetic resonance reveal a domino reduction pathway involving sequential proton-coupled electron and hydrogen-atom transfers through key intermediates (CO2•−, •COH and •CH2OH). This system achieves methanol synthesis without traditional solid catalysts or external bias, showcasing gas−water interfaces as dynamic, self-sustaining alternatives for CO2 conversion.