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.