The present invention relates to the selective separation of carbon dioxide (“CO2”) from methane (“CH4”) in streams containing both carbon dioxide and methane utilizing a zeolitic imidazolate framework (“ZIF”) material. Preferably, the stream to be separated is fed to the present process in a substantially gaseous phase. In preferred embodiments, the current invention is utilized in a process to separate carbon dioxide from natural gas streams preferably for sequestration of at least a portion of the carbon dioxide present in the natural gas.