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

Abstract

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.

Rational Tuning of Zirconium Metal–Organic Framework Membranes for Hydrogen Purification

“…However, due to the relatively large pore size (ca. 0.6 nm), the selectivity of UiO‐66 membrane follows the Knudsen selectivity values, that is, H 2 /CO 2 ≈5 …”

Rational Tuning of Zirconium Metal–Organic Framework Membranes for Hydrogen Purification

“…0.6 nm), the selectivity of UiO-66 membrane follows the Knudsen selectivity values,that is,H 2 /CO 2 % 5. [26] Taking advantage of Zr-MOFs,weused UiO-66 as abase material to fabricate polycrystalline membranes for hydrogen separation applications.Particularly,w edeveloped and characterized continuous UiO-66 membranes with as eries of linkers varying in size and functionalities to study avariety of different desired separations (Scheme 1). Furthermore,t he molecular gas diffusion through the MOF membranes was simulated based on density functional theory (DFT) to predict the effect of the structure of ligands and MOFs pore aperture on the gas separation performance of the membranes.T ot he best of our knowledge,t his work is the first report on the development and tuning of Zr-MOF membranes for hydrogen separation.…”

Mass transport through metal organic framework membranes

“…For example, the triangular pore entrance size of UiO-66 fluctuating between 3.7 and 9.2 Å results from the 3 orientable benzene rings performing flips around the C 2 symmetry axis, as shown in Fig. 7a [126]. In addition, the entrance sizes and the channel morphology of MOF in different orientation are not the same due to its anisotropy.…”