Fabrication of Highly Oriented Ultrathin Zirconium Metal-Organic Framework Membrane from Nanosheets towards Unprecedented Gas Separation

Concurrent regulation of crystallographic orientation and thickness of zirconium metal-organic framework (Zr-MOF) membranes is challenging but promising for their performance enhancement. In this study, we pioneered the fabrication of uniform triangular-shaped, 40 nm thick UiO-66 nanosheet (NS) seeds by employing an anisotropic etching strategy. Through innovating confined counter-diffusion-assisted epitaxial growth, highly (111)-oriented 165 nm-thick UiO-66 membrane was prepared. The significant reduction in thickness and diffusion barrier in the framework endowed the membrane with unprecedented CO2 permeance (2070 GPU) as well as high CO2/N-2 selectivity (35.4), which surpassed the performance limits of state-of-the-art polycrystalline MOF membranes. In addition, highly (111)-oriented 180 nm-thick NH2-UiO-66 membrane showing superb H-2/CO2 separation performance with H-2 permeance of 1230 GPU and H-2/CO2 selectivity of 41.3, was prepared with the above synthetic procedure.