Mixed matrix membranes for selective gas separation of H2/CH4 and CO2/CH4 via fabricating high-performing double-ligand ZIF-8 with cellulose acetate-based polymer

Abstract

ZIF-8-based mixed matrix membranes are most used for selective gas separation due to their obvious molecular sieving properties. However, their application remains challenging due to their incompatibility with polymer matrix. In this study, we introduced the AZIF-8 nanoparticles synthesized via partial substitution of 2-methyl imidazole (2-Mim) ligand by 3-amino-1, 2, 4-triazole (Atz) to finely tune the aperture and increase gas separation performance of MMMs. The integration of Atz ligand significantly enhances particle dispersion and compatibility with polymer. Different ligand substitution times and loadings were applied to investigate the gas separation performance. The experimental results reveal that the Atz modified ZIF-8 (AZIF-8) blended CA MMMs with 1 wt% loading showed the high separation activity. The A₈ZIF-8/CA (A₈ = 8 h) is able to achieve high H₂ and CO₂ permeability values of 183.5 and 135.0 Barrer, respectively, with ideal selectivity of 49.1 and 36.1 for H₂/CH₄ and CO₂/CH₄, respectively, under the 0.4 MPa feed pressure. Remarkably, the gas separation activity of Atz modified ZIF-8 MMMs lies very close to the Robeson upper bound 2008, signifying the effectiveness of the reported modification strategy.