Twinned Metal–Organic Framework Nanoplates for Hydrocarbon Separation Membranes.

Filler morphology control is critical for enhancing the gas separation performance of mixed matrix membranes (MMMs). A vertical transport channel using the crystal twinning phenomenon is designed on the zeolitic imidazolate framework (ZIF) nanoplate. Twinned ZIF‐8 (TZIF‐8) nanoplate is prepared by controlling the shape of ZIF‐L from nanosheet to twinned flake, followed by conversion into the ZIF‐8 phase. With the addition of TZIF‐8 in 6FDA‐DAM polymer, propylene/propane selectivity is dramatically enhanced, showing propylene permeability of 40 Barrer and propylene/propane selectivity of 82. The separation performance surpasses the performance of MMMs reported so far, and the selectivity is comparable to that of polycrystalline ZIF‐8 membranes. A transport mechanism study using mathematical models implies that the percolated twin fillers create rapid and selective gas channels for desired molecules and substantial tortuous pathways for undesired molecules. [ABSTRACT FROM AUTHOR]