Confinement-induced acceleration of CO2 mineralization through interfacial water thinning

Current projections demand atmospheric CO2 removal at the gigatonne-per-year scale through mineral carbonation, yet conventional aqueous routes remain energy-intensive and kinetically limited. Here we apply a water thinning strategy to engineer the interfacial water-film (IWF) with thicknesses below 8.5 nm. We achieve complete carbonation of calcium hydroxide (Ca(OH)2) within 1 h under ambient conditions, realizing a 16-fold acceleration compared to bulk solution systems. The IWF exhibits confinement-induced saturation kinetics, with the reaction rate increasing with CO2 partial pressure and then approaching a plateau around 2.02 kPa. Within this film, pocket-like sites in the water confined between particles use oriented interfacial hydroxyls to organize CO2 and ions, facilitating carbonation even at pCO2 as low as 0.04 kPa. Crucially, this IWF enables rapid carbonation of industrial alkaline wastes such as carbide slag under ambient conditions, obviating the requirement for pretreatment or other energy-intensive operations. Its demonstrated efficacy across different Ca-rich residues highlights its wide applicability and scalability for CO2 sequestration. Our findings establish water nanostructuring as a universal platform to unlock Earth-abundant minerals for scalable CO2 removal applications. Mineral carbonation offers a scalable route for CO2 removal. Here, the authors develop a water-thinning strategy to engineer confined interfacial sites that enable carbonation of calcium hydroxide under ambient conditions.