Rational Design of Mixed Matrix Membranes Modulated by Trisilver Complex for Efficient Propylene/Propane Separation

The application of membrane‐based separation processes for propylene/propane (C(3)H(6)/C(3)H(8)) is extremely promising and attractive as it is poised to reduce the high operation cost of the established low temperature distillation process, but major challenges remain in achieving high gas selectivity/permeability and long‐term membrane stability. Herein, a C(3)H(6) facilitated transport membrane using trisilver pyrazolate (Ag(3)pz(3)) as a carrier filler is reported, which is uniformly dispersed in a polymer of intrinsic microporosity (PIM‐1) matrix at the molecular level (≈15 nm), verified by several analytical techniques, including 3D‐reconstructed focused ion beam scanning electron microscropy (FIB–SEM) tomography. The π‐acidic Ag(3)pz(3) combines preferentially with π‐basic C(3)H(6), which is confirmed by density functional theory calculations showing that the silver ions in Ag(3)pz(3) form a reversible π complex with C(3)H(6), endowing the membranes with superior C(3)H(6) affinity. The resulting membranes exhibit superior stability, C(3)H(6)/C(3)H(8) selectivity as high as ≈200 and excellent C(3)H(6) permeability of 306 Barrer, surpassing the upper bound selectivity/permeability performance line of polymeric membranes. This work provides a conceptually new approach of using coordinatively unsaturated 0D complexes as fillers in mixed matrix membranes, which can accomplish olefin/alkane separation with high performance.