Engineering the Polymer–MOF Interface in Microporous Composites to Address Complex Mixture Separations
Wan‐Ni Wu, Katherine Mizrahi Rodriguez, Naksha Roy, Justin J. Teesdale, Gang Han, Alexander Liu, Zachary P. Smith
Abstract
Poor interfacial compatibility remains a pressing challenge in the fabrication of high-performance polymer–MOF composites. In response, introducing compatible chemistries such as a carboxylic acid moiety has emerged as a compelling strategy to increase polymer–MOF interactions. In this work, we leveraged compatible functionalities in UiO-66-NH 2 and a carboxylic acid-functionalized PIM-1 to fabricate mixed-matrix membranes (MMMs) with improved separation performance compared to PIM-1-based MMMs in industrially relevant conditions. Under pure-gas conditions, PIM-COOH-based MMMs retained selectivity with increasing MOF loading and showed increased permeability due to increased diffusion. The composites were further investigated under industrially relevant conditions, including CO 2 /N 2, CO 2 /CH 4, and H 2 S/CO 2 /CH 4 mixtures, to elucidate the effects of competitive sorption and plasticization. Incorporation of UiO-66-NH 2 in PIM-COOH and PIM-1 mitigated the effects of CO 2 - and H 2 S-induced plasticization typically observed in linear polymers. In CO 2 -based binary mixed-gas tests, all samples showed similar performance as that in pure-gas tests, with minimal competitive sorption contributions associated with the amine functional groups of the MOF. In ternary mixed-gas tests, improved plasticization resistance and interfacial compatibility resulted in PIM-COOH-based MMMs having the highest H 2 S/CH 4 and CO 2 /CH 4 selectivity combinations among the films tested in this study. These findings demonstrate that selecting MOFs and polymers with compatible functional groups is a useful strategy in developing high-performing microporous MMMs that require stability under complex and industrially relevant conditions.