With the upgrading of fermentative biogas to produce gaseous transport fuel, ionic liquid (IL) [P-66614] [2-Op], which adsorbed CO, through multiple-site cooperative interactions, was loaded onto molecular sieve MCM-41 to adsorb CO, in a biohythane atmosphere (CH4 + H-2 + CO2). [P-66614] [2-Op] loaded onto MCM-41 exhibited a higher CO, adsorption rate than pure IL during the initial stage because of its larger reaction surface area. However, the CO2 adsorption rate of [P-66614] [2-Op] loaded onto MCM-41 became lower than that of pure IL as the reaction continued because CO2 was inaccessible to the IL blocked within the inner pores of MCM-41. The CO2 adsorption rate of IL loaded onto the molecular sieve (MCM-41-50% IL) was (51.5 mg of CO2 CI of IL min(-1)) 2.1 times higher than that of pure IL during the initial 1 min in a pure CO2 atmosphere and was (24.6 mg of CO2 g(-1) of IL min(-1)) 2.2 times higher than that of pure IL during the initial 2 min in a biohythane atmosphere.