The　Al-pillared　montmorillonite-supported　alkaline　earth　metal　5M/Al-PILC　(PILC　=　pillared　clay,　M　=　Mg,　Ca,　Sr,　and　Ba)　and　xMg/Al-PILC　(x　=　1,3,5,　and　7　wt.%)　samples　were　prepared　using　an　impregnation　method.　Physical　properties　of　the　materials　were　determined　by　means　of　X-ray　diffraction　(XRD)　and　N-2　adsorption-desorption,　and　their　CO2　adsorption　behaviors　were　investigated　using　the　thermogravimetric　analyzer　(TG),　CO2　temperature　programmed　desorption　(CO2-TPD),　and　in　situ　diffuse　reflectance　infrared　transform　spectroscopy　(in　situ-DRIFTS)　techniques.　It　is　shown　that　5Mg/Al-PILC　possessed　the　highest　CO2　adsorption　capacity　(2.559　mmol/g).　The　characterization　results　indicate　that　Al　pillaring　increased　the　specific　surface　area　of　montmorillonite,　which　was　beneficial　for　the　adsorption　of　CO2.　The　CO2　adsorption　process　on　the　sample　was　mainly　chemical　adsorption,　and　alkalinity　was　the　main　factor　influencing　its　adsorption　capacity.　The　alkalinity　of　the　sample　was　enhanced　by　loading　an　appropriate　amount　of　alkaline　earth　metal,　and　the　adsorbed　CO2　was　present　in　the　form　of　bicarbonate　and　carbonate.　In　addition,　the　5Mg/Al-PILC　sample　exhibited　an　excellent　regeneration　efficiency.　We　believe　that　the　outcome　of　this　research　would　provide　a　good　option　for　developing　highly　effective　CO2　adsorption　materials.　(C)　2020　The　Research　Center　for　Eco-Environmental　Sciences,　Chinese　Academy　of　Sciences.　Published　by　Elsevier　B.V.