Yeonbhin Kim

1 Introduction Energy efficient and environment friendly CO2 removal from methane-rich off-gas or recycled streams is essential in various industrial processes including biogas upgrading, natural gas sweetening, and the purification of unreacted methane from reforming or separation units [1, 2]. Conventional CO2/CH4 separation technologies such as cryogenic distillation or amine scrubbing are highly energy-intensive.