Sustainable Thin Film Composite Mixed Matrix Membranes Based on Cellulose Acetate, Bimetallic ZIF-8-67 and Ionic Liquid for Enhanced Propene/Propane Separation

Efficiently separating propene and propane is paramount for the chemical industry but notoriously difficult due to their minimal size and volatility differences. Here, we demonstrate a powerful strategy to overcome this separation challenge by designing bimetallic Zeolitic Imidazolate Framework (ZIF)-based mixed-matrix membranes (MMMs). We fabricated thin-film composites (TFCs) by integrating monometallic ZIF-8, ZIF-67, and a synergistic bimetallic ZIF-8-67 into a uniquely formulated ionic liquid-cellulose acetate (IL-CA) polymer matrix. Structural and morphological analyses confirmed the high crystallinity of the ZIF fillers and their seamless integration within the polymer. The resultant ZIF-8-67/IL-CA membrane exhibited exceptional separation performance, surpassing its monometallic counterparts by a threefold increase in both C3H6 permeance and C3H6/C3H8 ideal selectivity relative to the base membrane. Under industrially relevant mixed-gas testing, the membrane achieved an impressive separation factor of 8 for propene over propane. These findings reveal that the strategic integration of bimetallic nodes in ZIFs can unlock synergistic properties unattainable with single-metal frameworks. This work presents a robust and scalable platform for developing next-generation membranes that defy conventional performance trade-offs, a way for efficient membrane-based olefin/paraffin separations.