CO2 separation from gas mixtures using graphene and carbon nanotubes-based membranes: A review on recent progresses and outlooks

Carbon dioxide (CO2) emissions to the atmosphere are rapidly increasing, resulting in global warming and climate change, which in turn, could lead to undesirable and disastrous environmental outcomes. To sustain human civilization on Earth, effective measures for managing CO2 emissions have to be urgently developed and implemented. Membrane separation represents an attractive approach for CO2 elimination from gaseous streams generated in various industries. However, membranes fabricated from conventional materials are usually ineffective and/or suffer from several drawbacks. Recently, carbon nanotubes (CNTs) and graphene have emerged as attractive materials for the fabrication of effective membranes (including, mixed matrix membranes, abbreviated as MMMs) due to their robustness, excellent mechanical strength, high porosity, durability, tunability, and ease of functionalization with different functional materials. Additionally, membranes fabricated using thin films of CNTs and graphene-based materials via techniques such as phase inversion, electrospinning, interfacial polymerizations, and sol-gel processes, have the potential to improve the CO2 separation efficiency (i.e., permeability and selectivity). Furthermore, incorporating CNTs and graphene-based materials into composite and nano-composite membranes could boost their effectiveness in CO2 separation from complex gas mixtures. Such technological advancements will enhance the realization of CO2 membrane separation processes. Accordingly, this article focuses on comprehensively reviewing recent progresses in the fabrication of graphene and CNTsbased membranes and their application for CO2 separation from various gas mixtures. After a brief overview of the synthesis methods of CNTs and graphene-based materials, their functionalization and utilization for membrane fabrication, and CO2 separation using these membranes will be thoroughly reviewed. Additionally, the long-term stability and durability of these membranes under various process conditions will be discussed. Furthermore, the performance of these membranes in separating CO2 from gas mixtures is compared to those of zeolitic and polymeric-based membranes. Key challenges and obstacles facing CO2 separation using graphene and CNTs-based membranes are also discussed, and future research work to address them is highlighted. To the best of our knowledge, recent and comprehensive reviews focusing on CO2 separation using graphene and CNTsbased membranes are still limited in the published literature, highlighting the novelty and the need for recent and comprehensive reviews as the one presented herein.