Advanced polymeric membranes for CO2 separation: fundamentals, materials, and practical challenges

Abstract

Membrane-based CO2 separation is emerging as a central technology for achieving carbon neutrality, yet its widespread deployment remains constrained by longstanding trade-offs among permeability, selectivity, long-term stability, and scalability. This review provides the conceptual foundations, materials evolution, and market drivers shaping the next generation of polymeric CO2 separation membranes. We first revisit the fundamentals of mass transport through dense polymer films and highlight how trade-offs arise from the interplay among solubility, diffusivity, and free-volume architecture. Building on this framework, we examine three major materials platforms that have redefined performance boundaries: thermally rearranged (TR) polymers that generate controlled microporosity through in situ cyclization; polymers of intrinsic microporosity (PIMs) that embody rigid, contorted backbones with permanent ultramicroporosity; and ether-rich CO2-philic polymers that achieve high solubility selectivity and excellent processability. By integrating molecular-level insights with thin-film engineering considerations, we evaluate each material family's potential and limitations in realistic process environments. At the system level, we analyze global markets, including natural gas sweetening, post-combustion CO2 capture, blue hydrogen purification, and biogas upgrading, where polymeric membranes are poised for rapid growth. Finally, we identify future research directions centered on stabilizing free volume, suppressing plasticization, enhancing thin-film robustness, and accelerating materials-to-module translation through digital design and advanced fabrication. Together, these strategies delineate a pathway for polymeric membranes to become scalable, energy-efficient tools for industrial CO2 management in the coming decade.