The aims of this work were to synthesize the porous solid adsorbents and to study their carbon dioxide (CO 2) adsorption capacities. Three adsorbents; activated carbon synthesized from bagasse (BAC) and from rice husk (RAC), and Mobil Composition of Matter number 41 (MCM-41) from rice husk silica (R-MCM-41) were investigated. The synthesized BAC, RAC and R-MCM-41 showed high thermal stability with the weight loss less than 0.1% for the temperatures below 150°C. N 2 adsorption isotherm analysis indicates that BAC and RAC are microporous while R-MCM-41 is mesoporous materials. The BET surface areas were 923, 927 and 602 m 2 g-1 for BAC, RAC and R-MCM-41, respectively. The total pore volumes were 0.53, 0.56 and 0.49 cm 3 g-1 , and pore sizes were 0.8, 0.8, and 2.43 nm for BAC, RAC and R-MCM-41, respectively. At 30°C these materials were able to adsorb 76.89, 57.13 and 23.32 mg-CO 2 g-1-adsorbent, respectively. When the adsorption temperature increased, adsorption capacity of BAC, RAC and R-MCM-41 was decreased. This implied that physical process was the main mechanism of CO 2 adsorption.