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Carbon dioxide (CO₂) capture and storage (CCS) is an important climate change mitigation option along with improved energy efficiency, renewable energy, and nuclear energy. CO₂ geosequestration, that is, to store CO₂ under the subsurface of Earth, is feasible because the world’s sedimentary basins have high capacity and are often located in the same region of the world as emission sources. How CO₂ interacts with the connate water and minerals is the focus of this Account. There are four trapping mechanisms that keep CO₂ in the pores of subsurface rocks: (1) structural trapping, (2) residual trapping, (3) dissolution trapping, and (4) mineral trapping. The first two are dominated by capillary action, where wettability controls CO₂ and water two-phase flow in porous media. We review state-of-the-art studies on CO₂/water/mineral wettability, which was found to depend on pressure and temperature …