Fabrication of Ultrathin Membranes Using 2D-MOF Nanosheets for Tunable Gas Separation

Graphical In this work, we report the fabrication of ultrathin and defect-free Zr-BTB membranes constructed by the assembly of monolayer MOF nanosheets with tunable gas separation performance. H 2 /CO 2 selectivity of the membranes can be enhanced by increasing the membrane thickness or by introducing the thermal disturbance during the membrane fabrication process. Two-dimensional (2D) metal-organic frameworks (MOF) nanosheets have emerged as novel membrane materials for gas separation. However, the development of ultrathin MOF membranes with tunable separation performances is still a challenge. Herein, we developed a facile GO-assisted restacking method to fabricate defect-free membranes with monolayer Zr-BTB nanosheets. Obtained ultrathin membranes ranging from 130 nm to 320 nm show tunable separation performances and exceed the 2008 Robeson upper bound by changing the amount of nanolayers in vertical stacking direction. Furthermore, a heating filtration method was used to change the restacking process of nanosheets in the horizontal direction. As a result, H 2 /CO 2 selectivity can be enhanced by two times with the same membrane thickness (130 nm) and H 2 permeance is almost maintained to be 7.0×10 −7 mol m −2 s −1 pa −1 . This method may provide a possible way to efficiently tune the gas separation performances of MOF membranes.