Non-Covalent Cross-Linking Does the Job: Why PIM-1/Silicalite-1 Mixed Matrix Membranes Perform Well Notwithstanding Silicalite-1.

The macroscopic modeling of gas transport in mixed-matrix membranes (MMMs) made of a Polymer of Intrinsic Microporosity (PIM-1) and silicalite1 (MFI) is compared to the experimental results presented in a previous paper, which shows unexpectedly large gas separation factors, although the silicalite-1 filler is practically nonselective. The mismatch between the predictions of the Maxwell model and the experiments is zeroed by the recognition of nonideal effects, the extent of which is evaluated. The good performance of the PIM-1 MMM is explained by non-covalent cross-linking of the PIM-1 matrix. Cross-linking results from π-π stacking interactions between the 2-phenylethyl grafts on the outer surface of the MFI crystals and the aromatic ladder segments of PIM-1, in agreement with the current explanation of the good transport performance of PIM-1 MMMs containing porous aromatic fillers (e.g., PAF-1).