Zirconia nanoparticles modified by barium oxide or magnesium oxide were synthesized by using a co-precipitation process followed by ethanol supercfitical drying. The nanoparticles obtained were further calcined at 873 K. BET surface area, XRD, and TGA were used to characterize the prepared samples. Isotherms of N-2 and CO2 adsorption on these modified zirconia nanoparticles were measured at various temperatures. Additions of BaO or MgO resulted in an increase in CO2 adsorption capacity of the modified zirconia particles. Results also show that BaO as a modifier is more effective than MgO in enhancing the CO2 adsorption capacity of zirconia. At 1 bar and 473 K, Ba modified zirconia adsorbs similar to 0.25 mmol/g of CO2. (c) 2004 Elsevier Inc. All rights reserved.