The development of novel sorbents for reducing the carbon dioxide emissions at high temperature focused on cesium-doped CaO sorbents with respect to other major flue gas compounds in a wide temperature range has been studied in this paper. The sorbent calcined under oxygen atmosphere leads to the formation of cesium superoxide (CsO2) on the sorbent surface. The thermogravimetric analysis of sorbent with 20 wt % cesium loading on CaO demonstrated a CO2 sorption uptake of 66 wt % CO2/g of sorbent. It is remarkable to note that zero adsorption affinity for N-2 and O-2 at temperatures as high as 600 degrees C was observed. This is due to the presence of highly oxidized phase of cesium (CsO2) on the sorbent surface and the sorbent being unable to react with nitrogen at the above-mentioned temperatures. In the presence of water vapor, the adsorption Of CO2 increased to the highest capacity of 77 wt % CO2/g of sorbent. The reason for this behavior is that the water vapor digs into the bigger particles, thus making the porous type of sorbent material. In the presence of nitrogen oxide, the final CO2 adsorption remained the same, but the rate of adsorption was higher at the initial stages (10%) than the case where no nitrogen oxide was fed.