Bifunctionalized NH 2 -UiO-66-CF 3 mixed matrix membranes for gas separation

Abstract

Bifunctionalized NH₂-UiO-66-CF₃ nanofillers were successfully prepared by grafting - CF₃ on NH₂-UiO-66 via aldehyde-amine condensation reaction and applied to the preparation of 6FDA-ODA/NH₂-UiO-66-CF₃ mixed matrix membranes (MMMs). The successful introduction of -NH₂ and -CF₃ groups was verified by FT-IR, XRD, and XPS characterization, and the integrity of the crystal structure was ensured. Due to the presence of hydrogen bonding, NH₂-UiO-66-CF₃ showed good interfacial compatibility with the polymer matrix. Due to the introduction of the - CF₃ group, the MMMs exhibited excellent thermal stability (T_10% > 500°C, T_g = 300°C–305°C), hydrophobicity (contact angle of 92.96–97.71), and mechanical properties (tensile strength of 74–85 MPa). The gas separation performance tests showed that the MMMs exhibited significantly improved gas permeability and selectivity compared to the pure 6FDA-ODA membranes, which was attributed to the fact that the -NH₂ and -CF₃ groups provided more adsorption sites for gases. In particular, the PI/NUF(10) MMMs showed the best performance, with permeabilities of 42.71, 9.22, and 92.79 Barrer for CO₂, O₂, and He, respectively, which were 248%, 213%, and 173% higher than those of the pure membranes. Meanwhile, the selectivities of CO₂/N₂, O₂/N₂ and He/N₂ were improved by 37%, 24%, and 8%, respectively. Close to the Robeson upper limit, demonstrating excellent gas separation potential.