The invention relates to a mixed salt composition which is useful as a CO2 sorbent. The mixed salt composition comprises a Mg salt, and at least one Group IA element salt, where the Mg and Group IA element are present at a molar ratio of from 3:1 to 8:1. The resulting composition can adsorb about 20% or more of CO2 in a gas. Via varying the molar ratios of the components, and the Group IA element, one can develop compositions which show optional functionality at different conditions. The composition is especially useful in the adsorptive capture of CO2 on mobile sources, such as transportation vehicles, where it can be recovered during regeneration of the adsorbent composition and the CO2 used as a coolant gas, as a reactant in manufacture of fuel, and so forth.
