Metal-Organic Framework UiO-66 Layer: A Highly Oriented Membrane with Good Selectivity and Hydrogen Permeance.

The 3D metal-organic framework (MOF) structure UiO-66 [ZrO(OH)(bdc)], featuring triangular pores of approximately 6 Å, has been successfully prepared as a thin supported membrane layer with high crystallographic orientation on ceramic α-AlO supports. The adhesion of the MOF layer to the ceramic support was investigated in different taxing conditions. Furthermore, by coating this UiO-66 membrane with a thin polyimide (Matrimid) top layer, we prepared a multilayer composite. Said membranes have been evaluated in the separation of hydrogen (H) from different binary mixtures at room temperature. H as the smallest molecule (2.9 Å) should pass the UiO-66 membrane preferably since the kinetic diameters of all the other gases under study are larger. The gas mixture separation factors for the neat UiO-66 membrane were indeed found to be H/CO = 5.1, H/N = 4.7, H/CH = 12.9, H/CH = 22.4, and H/CH = 28.5. The coating with Matrimid led to a sharp cutoff for gases with kinetic diameters greater than 3.7 Å, resulting in increased separation performance.