A reaction-based process has been developed for the selective removal of carbon dioxide from a multicomponent gas mixture. The proposed process effects the separation of CO.sub.2 from a mixture of gases by its reaction with metal oxides. The Calcium based Reaction Separation for CO.sub.2 process consists of contacting a CO.sub.2 laden gas with calcium oxide in a reactor such that CaO captures the CO.sub.2 by the formation of calcium carbonate. Once "spent", CaCO.sub.3 is regenerated by its calcination leading to the formation of fresh CaO sorbent. The "regenerated" CaO is then recycled for the further capture of more CO.sub.2. This process also identifies the application of a mesoporous CaCO.sub.3 structure, that attains >90% conversion over multiple carbonation and calcination cycles. Lastly, thermal regeneration (calcination) under vacuum provided a better sorbent structure that maintained reproducible reactivity levels over multiple cycles.