Interaction of carbon dioxide with Na-exchanged montmorillonite at pressures to 640Â bars: Implications for CO2 sequestration

► Na-exchanged montmorillonite forms an intercalate with CO2. ► Intercalation of CO2 depends on the clay's initial H2O content. ► The formation of the CO2 intercalate is complete by ∼50 bars pressure. ► Maximum expansion was approximately 10%.