Scalable Pillar[5]arene-Integrated Poly(arylate-amide) Molecular Sieve Membranes to Separate Light Gases

Molecular sieve membranes and their analogues could potentially transform energy-intensive gas separation processes. However, many such membranes suffer from either limited processability or physical stability including plasticization of semi-flexible microstructures. Here, we report on a new variation of all-polymer-based molecular sieve membranes that could tackle these specific challenges. These membranes were prepared by the interfacial polymerization of pillar[5]arene, m-phenylenediamine, and trimesoyl chloride to create characteristic poly(arylate-amide) heteropolymer microstructures. Pillar[5]arenes were crosslinked into the films with net weight fractions of up to ∼47%, wherein the 4.7 Å cavities of pillar[5]arenes were interconnected with ∼2.8 Å apertures. These microstructures provided preferred permeation paths for smaller molecules (He and H₂) among the tested light gases (He, H₂, CO₂, O₂, N₂, and CH₄) and resulted in significant molecular sieving effects with representative pure gas selectivities of 32 (H₂/CO₂), 150 (CO₂/CH₄), 4600 (H₂/CH₄), 13 (O₂/N₂), and 4.7 (N₂/CH₄) at 35 °C and 10 atm. These separation factors outperform most polymer-based gas separation membranes, while providing membrane features such as thin film barriers, cross-linked polymer backbones, and excellent processability resulting from interfacial polymerization that are critical for large-scale operations.