(507g) Highly Selective and Stable Thin-Film Composite Membranes Based on Hyper-Crosslinked Spirocyclic Polymers for CO2 Separation

Thin film composite membranes exhibiting high CO₂ selectivity and long-term stability against physical aging and plasticization are sought to replace conventional separation processes.

In this work, a new family of hyper-crosslinked spirocyclic polymer membranes, purposely designed to resist plasticization and maintain their separation efficiency under the harshest chemical conditions, was fabricated as thin film composite membranes and tested for CO₂ separation at high pressure and under complex gas mixtures.

The membrane structure was investigated via SEM, XRD, and PALS, showing that defect-free selective layers, as low as 300 nm thin, can be fabricated via a simple spin-coating process.

Permeability and selectivity under binary CO₂/CH₄ and ternary CO₂/CH₄/C₂H₆ mixtures exhibiting different compositions were experimentally measured, correlated to the material structure and compared with state-of-the art-materials. Notably, a mixed-gas selectivity as high as 70 was achieved. Plasticization and aging under pure- and mixed-gas conditions were also investigated, pointing out an almost unprecedented stability under the harshest operating conditions.

The role of pure- and mixed-gas sorption and diffusion selectivity on the total apparent selectivity was elucidated.

Finally, the behavior of thin-film composite membranes was compared vis-à-vis with that of bulky, free-standing films.