Calcium oxide based materials are attractive regenerable absorbents for separating CO{sub 2} from hot gas streams because of their high reactivity, high CO{sub 2} capacity, and low material cost. Their high carbonation temperature makes it possible to recover and use high quality heat released during CO{sub 2} capture, which increases overall process efficiency. However, the performance of all reported CaO-based absorbents deteriorates as the number of carbonation-decarbonation cycles increases. This is caused by absorbent sintering during the highly exothermic carbonation process. We have found that sintering can be effectively mitigated by properly mixing with a modest amount of MgO. A class of CaO-based absorbents with improved durability and CO{sub 2} reactivity were prepared by physical mixing of Ca(CH{sub 3}COO){sub 2} with small MgO particles followed by high temperature calcination. With 26 wt % MgO content, a CaO-MgO mixture prepared by this method gives as high as 53 wt % CO{sub 2} capacity after 50 carbonation-decarbonation cycles at 758{sup o}C. Without MgO addition, the CO{sub 2} capacity of pure CaO obtained from the same source decreases from 66 wt % for the first cycle to 26 wt % for the 50th cycle under the same test conditions.