Design of Mixed-Matrix MOF Membranes with Asymmetric Filler Density and Intrinsic MOF/Polymer Compatibility for Enhanced Molecular Sieving

by Rifan Hardian, Jiangtao Jia, Alejandro Diaz-Marquez, Supriyo Naskar, Dong Fan, Osama Shekhah, Guillaume Maurin, Mohamed Eddaoudi, Gyorgy Szekely
Year: 2024 DOI:


The separation of high-value-added chemicals from organic solvents is of prime importance for many industries but it is associated with a large energy consumption penalty. Suitably, membrane-based nanofiltration offers potential for a more energy-efficient separation than the conventional energy-intensive thermal processes. Conceivably, mixed-matrix membranes (MMMs), encompassing metal–organic frameworks (MOFs) as fillers, are poised to promote selective separation via molecular sieving, synergistically combining polymers flexibility and fine-tuned porosity of MOFs. Nevertheless, conventional direct mixing of MOFs with polymer solutions results in underutilization of the MOF fillers owing to their uniform cross-sectional distribution. Therefore, in this work, we propose a multizoning technique for the formation of MMMs with an asymmetric-filler density at the macroscale, in which the MOF fillers are distributed only on the surface of the membrane, and a seamless interface at the nanoscale. Our design strategy demonstrates five times higher MOF surface coverage, which results in a solvent permeance five times higher than that of conventional MMMs while maintaining high selectivity. Practically, MOFs are paired with polymers of similar chemical nature in order to enhance their adhesion without the need for additional surface modification. Our approach offers permanently accessible MOF porosity, which translates to effective molecular sieving, as exemplified by the polybenzimidazole and Zr–BI–fcu-MOF system. Our findings pave the way for the development of composite materials with a seamless interface.