Freestanding, Self-Healing CO ₂ Separation Nanomembranes Based on PEG-Linked α-Lipoate Networks

The development of high-performance CO2 separation membranes is essential for advancing energy-efficient CO2 capture technologies. Herein, we present self-healing nanomembranes composed of network polymers derived from polyethylene glycol (PEG)-linked bifunctional α-lipoate monomers and disulfide-based cross-linkers. The polymer networks were formed via base-catalyzed ring-opening polymerization (ROP) of bifunctional monomers in the presence of pentaerythritol tetra(3-mercaptopropionate) (PTM), yielding membranes with a thickness of approximately 200–500 nm and tunable cross-linking density. Systematic evaluation revealed a trade-off relationship between PTM content and gas permeability, with membranes exhibiting a CO2 permeance of 470 GPU and a CO2/N2 selectivity of 58. Further enhancement of the CO2 permeance was achieved by membrane thinning. With a 36 nm-thick membrane, the CO2 permeance was 950 GPU without sacrificing the selectivity of 45. Differential scanning calorimetry (DSC) confirmed that a higher chain mobility correlates with improved gas transport properties. Moreover, the network polymer exhibited an intrinsic self-healing ability, as evidenced by the thermal reconnection of a cut film and the fusion of two partially overlapped membranes at 45 °C.