Potential applications of MOF composites as selective membranes for separation of gases

Gas separation, which involves extracting one or more gases from a gas mixture, is a crucial technique in the chemical industry. Many separation techniques have been documented, but one of the prevalent methods is the use of membrane technology to separate gases. Separating gases through membranes is accomplished via various transport mechanisms of different gases. Compared to other gas separation methods, membrane gas separation offers the significant benefit of potentially reducing energy consumption. Reaching such potential calls for developing the membranes that exhibit greater stability, selectivity and permeability than the ordinary membranes being used such as zeolites and polymers. Metal-organic framework (MOF) composites because of their unique chemical and physical properties and also thanks to the functional guests embedded in their structure fulfill the mentioned requisite to a large extent. However, applying MOF composites as membrane in gas mixture separation faces some disadvantages. For example, the compounds of MOF composites are expensive and their shaping process is not cost-effective. The present review presents the latest developments of MOF composites for selective gas separation (except carbon dioxide gas) including the application of MOF composites in hydrogen recovery, air separation, purification of natural gas, hydrocarbon separation and separation of toxic gases. Moreover, it discusses the factors improving the efficiency of such membranes for gas separation. Finally, a summary and a conclusion of the discussions are presented, as well as a future outlook of applying MOF composites in selective gas separation. We firmly believe that the present study proposes some unique promising ideas for logical design of certain MOF composites allowing selective separation of gases.