Fabrication of MIL-96 nanosheets and relevant c-oriented ultrathin membrane through solvent optimization

Concurrent manipulation of orientation and thickness of MOF membranes has become a reliable approach for improving their separation performances. In terms of oriented seeded growth, oriented deposition of MOF nanosheets during seeding process and sealing all intergranular gaps with no discernible increase in membrane thickness during secondary growth have become indispensable. In this study, we pioneered the fabrication of uniform hexagonal-shaped, 20–40 nm thick MIL-96 nanosheets through solvent composition optimization (VH2O/VFA = 1/2). Subsequently, spin coating was employed for c-oriented deposition of uniform MIL-96 seed layer, during which the addition of PVP in the suspension was found to be critical for obtaining qualified seed layer. Finally, well-intergrown, highly c-oriented ultrathin MIL-96 membrane was prepared upon employing NMF as the solvent during secondary growth. Gas permeation results implied that prepared MIL-96 membrane exhibited superior gas separation performance compared with that of a-&b-oriented counterpart.