English
Separating high value-added chemicals from organic solvents is important for many industries. Compared with traditional thermal processes, membrane based nanofiltration provides more energy-efficient separation. It can be imagined that mixed matrix membranes (MMM) containing metal organic frameworks (MOFs) as fillers are expected to promote selective separation through molecular sieves, synergistically combining the flexibility of polymers and the fine tuned porosity of MOFs. However, the traditional method of directly mixing MOFs with polymer solutions results in insufficient utilization of MOF fillers due to their uniform cross-sectional distribution. Therefore, in this work, a multi partition technique was proposed to produce MMM with asymmetric packing density, where MOF packing is only distributed on the surface of the membrane and has seamless interfaces at the nanoscale. This design strategy demonstrates a fivefold increase in MOF surface coverage, which results in a fivefold increase in solvent permeability compared to traditional MMM while maintaining high selectivity. In fact, MOFs are paired with polymers with similar chemical properties to enhance their adhesion without the need for surface modification. This method provides permanently accessible MOF porosity, which can be converted into effective molecular sieving, as shown in polybenzimidazole and Zr BI fcu MOF systems. These findings pave the way for the development of composite materials with seamless interfaces.
