Mixed matrix membranes incorporating two-dimensional ZIF-8 nanosheets for enhanced CO2/N2 separation

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-02, Vol.481, p.148294, Article 148294
• Main Authors: Jeong, Sung Kuk, Jeong, Jeong Yun, Lim, Semin, Kim, Woo-Sik, Kwon, Hyuk Taek, Kim, Jinsoo
• Format: Article
• Language: English
• Subjects: 2D ZIF-8; CO2/N2 separation; Mixed matrix membrane; Orientation control
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2023.148294

[Display omitted] •ZIF-8 nanosheets were synthesized by the surfactant-assisted hydrothermal method.•The nanosheets were mainly exposed with small 4 M window on basal planes.•The nanosheets enhanced diffusion-based CO2/N2 separation performance of MMMs.•The enhancement likely stemmed from smaller 4 M window than conventional 6 M window.•Both symmetric and TFC MMMs outdid most of the reported for CO2/N2 separation. In this report, a few unit-cell thick ZIF-8 nanosheets with (002) basal planes exposed with 4-membered windows were synthesized by using sodium dodecyl sulfate, an anionic surfactant as a structure directing agent, which were used as fillers to fabricate mixed matrix membranes (MMMs) for CO2/N2 separation. The 2D ZIF-8 fillers contributed to not only decreasing transport resistance due to highly porous nature but also strengthening CO2/N2 diffusive separation of the MMMs due to keen molecular sieving through 4-membered windows, smaller than conventional 6-membered windows of ZIF-8. Aligned filler dispersion in out-of-plane direction was maintained up to 10 wt% filler loading and the MMM with 10 wt% filler loading showed optimal performance of CO2 permeability of ∼350 Barrer and CO2/N2 selectivity of ∼94, outperforming most of the reported 2D nanosheet-based MMMs in addition to exceeding the 2019 upper bound. To check commercial viability, thin film nanocomposite (TFN) membranes composed of a skin layer of ∼780 nm including 10 wt% filler loading were prepared. The TFN membranes exhibited CO2 permeance of ∼710 GPU and CO2/N2 selectivity of ∼77, which surpasses most of state-of-the-art polymeric thin film composite (TFC) and TFN membranes especially in terms of selectivity.