Vapor Phase Infiltration of Metal Oxides into Nanoporous Polymers for Organic Solvent Separation Membranes

Membrane-based organic solvent separations promise a low-energy alternative to traditional thermal separations but require materials that operate reliably in chemically aggressive environments. While inorganic membranes can withstand demanding conditions, they are costly and difficult to scale. Polymeric membranes, such as polymer of intrinsic microporosity 1 (PIM-1), are easily manufactured into forms consistent with large-scale separations (e.g., hollow fibers) but perform poorly in aggressive solvents. Here, a new postfabrication membrane modification technique, vapor phase infiltration (VPI), is reported that infuses PIM-1 with inorganic constituents to improve stability while maintaining the polymer's macroscale form and nanoporous internal structure. The atomic-scale metal oxide networks within these hybrid membranes protect PIM-1 from swelling or dissolving in solvents. This stability translates to improved separation performance in a variety of solvents, including solvents capable of dissolving PIM-1. The infiltrated inorganic phase also appears to give new control over solute sorption in organic solvent nanofiltration (OSN). These hybrid membranes further show promising performance for organic solvent reverse osmosis (OSRO) separations in challenging solvents, even at small-molecular-weight differentials (14 Da). Because the VPI process can be integrated with state-of-the-art membrane modules, this treatment could be readily adopted into the large-scale manufacturing of advanced membranes.