In the present work, new CaO-based adsorbents were obtained by a fast solution combustion method and high-energy ball-milling process to study their CO₂ capture behavior under different moderate pressure and temperature conditions. The as-prepared CaO products were characterized systematically using different analytical techniques such as X-ray diffraction, scanning electron microscopy and N₂ physisorption measurements. The results showed that the CaO prepared by solution combustion and ball-milled during 2.5 h showed the maximum CO₂ adsorption capacity of 9.31 mmol/g at 25 °C and 1 atm mainly via chemisorption with CaCO₃ formation, which was corroborated by infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy studies. In general, the obtained results revealed that the synthesized CaO nanopowders from solution combustion that were treated by high-energy ball-milling enhanced their CO₂ adsorption capacity due to improved structural and textural properties, and this CaO-based adsorbent can be used as a promising material for CO₂ capture in post-combustion CO₂ capture technologies on a large scale, under atmospheric pressure and temperature conditions.