In-situ formation of asymmetric thin-film, mixed-matrix membranes with ZIF-8 in dual-functional imidazole-based comb copolymer for high-performance CO2 capture

Despite numerous studies on free-standing, mixed-matrix membranes (MMMs), the development of thin-film MMMs with high permeance is still an ongoing challenge. Here, the successful fabrication of ultra-highpermeance thin-film MMMs on a porous polymer substrate is described based on a highly porous zeolitic imidazole framework (ZIF-8) and a dual-functional imidazole-based comb copolymer. The copolymer of poly (vinyl imidazole)-poly(oxyethylene methacrylate) (PVI-POEM) is synthesized via free-radical polymerization, and it exhibits CO2-philicity, strong adhesion, and good interactions with fillers. In contrast to commercial benchmark membranes such as Pebax, the use of the PVI-POEM comb copolymer results in significant improvement in the CO2 permeance without significant loss of selectivity even at high ZIF-8 loadings and low thickness. It is attributed to the in-situ formation of inverse, asymmetric morphology of MMMs and partial infiltration of PVI-POEM chains into ZIF-8 particles. Optimization of the preparation process, such as ZIF-8 loading, substrate type, and coating layer thickness, leads to an extremely high CO2 permeance of 4474 GPU with high CO2/N-2 and CO2/CH4 ideal selectivities of 32.0 and 12.4, respectively, which is far beyond the current trade-off limit for membranes. The mechanism behind the exceptionally high CO2 separation performance is delineated by exploring molecular dynamic simulation through morphology, structural, and energetic analyses.

Automated summary

The study successfully fabricated ultra-high permeance thin-film mixed-matrix membranes using highly porous ZIF-8 and a dual-functional imidazole-based comb copolymer. Through optimization of the preparation process, it achieved extremely high CO2 permeance, high CO2/N-2, and CO2/CH4 ideal selectivities.