Whereas the importance of shale oil and gas production to the energy supply is increasing, the recovery of shale oil and gas is low and the environmental performance needs improvement. Injection of CO2 captured from industrial emitters into shale reservoirs could enhance the oil and gas recovery and retain CO2 through adsorption in shale to offset greenhouse gas emissions. In this work, we present a study on adsorption of CO2 in an organic-rich shale. Unusual adsorption behaviors have been observed: The rate of adsorption increased with increasing pressure without showing a trend of saturation. Moreover, mass loss occurred at an elevated pressure. The adsorption behaviors have been elucidated by extraction of hydrocarbons from shale by CO2, from which the interactions of CO2 with hydrocarbons are elucidated and new insights are obtained.