MXene assisted preparation of well-intergrown ZIF-67 membrane for helium separation.

Well-intergrown ZIF-67 membranes were prepared by the assistance of laminarly stacked MXene films. Several analytic methods have found that the MXene films, despite being as thin as 90 nm, could host a high amount of Co (II) ions. The Co (II)-MXene films acted as buffer layer and provided anchor sites for nucleation. After solvothermal synthesis, well-intergrown ZIF-67 membranes with a thickness about 4 μm were formed on Co (II)-MXene modified α-Al 2 O 3 disks. Single-gas and mixed-gas permeation experiments showed that the ZIF-67 membranes exhibited excellent gas separation performance and long-term chemical (against CO 2 and H 2 O) and thermal stabilities with a He permeance greater than 6.6 × 10−8 mol m–2 s–1 Pa–1 and selectivities above 13 for the gas mixtures He/N 2 and He/CH 4 , superior to the state-of-the-art MOF membranes. [Display omitted] • Cobalt ions are absorbed and intercalated into a 90 nm thick MXene film. • Co (II)-MXene films promote heterogeneous nucleation of ZIF-67. • Well-intergrown ZIF-67 membranes are prepared on MXene covered Al 2 O 3 supports. • MXene assisted ZIF-67 membranes exhibit excellent helium separation performance. [ABSTRACT FROM AUTHOR]