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Abstract Vapor phase ligand treatment (VPLT) of 2‐aminobenzimidazole (2abIm) for 2‐methylimidazole (2mIm) in ZIF‐8 membranes prepared by two different methods (LIPS: ligand induced permselectivation and RTD: rapid thermal deposition) results in a notable shift of the molecular level cut‐off to smaller molecules establishing selectivity improvements from ca. 1.8 to 5 for O₂/N₂; 2.2 to 32 for CO₂/CH₄; 2.4 to 24 for CO₂/N₂; 4.8 to 140 for H₂/CH₄and 5.2 to 126 for H₂/N₂. Stable (based on a one‐week test) oxygen‐selective air separation performance at ambient temperature, 7 bar(a) feed, and 1 bar(a) sweep‐free permeate with a mixture separation factor of 4.5 and oxygen flux of 2.6×10⁻³ mol m⁻² s⁻¹is established. LIPS and RTD membranes exhibit fast and gradual evolution upon a 2abIm‐VPLT, respectively, reflecting differences in their thickness and microstructure. Functional reversibility is demonstrated by showing that the original permeation properties of the VPLT‐LIPS membranes can be recovered upon 2mIm‐VPLT. 

This study addresses the challenge of generalizable fabrication of metal‐organic framework (particularly zeolitic imidazolate frameworks (ZIF)) hollow fiber membranes that can allow a broader range of separations including hydrocarbon (“petrochemical”) as well as organics/water (“biorefining”) separations. We report a novel strategy that combines fluidic membrane processing with chemically inert carbon hollow fibers to produce robust ZIF membranes. Macroporous carbon hollow fibers are successfully fabricated by pyrolytic conversion of cross‐linked polymer hollow fibers. This step allows the use of a wide range of relatively aggressive fluidic processing solvents and conditions. Using these inert fiber supports, the fabrication of ZIF‐90 membranes is demonstrated and their butane isomer separations are investigated for the first time. Furthermore, ZIF membranes on carbon hollow fibers can be used in the separation of water/organic mixtures without the issue of fiber swelling or dissolution as seen in ZIF/polymer hollow fiber membranes. ZIF‐8/carbon membranes show stable operation spanning several days for dehydration of furfural and ethanol, with high water permeances and separation factors. In all cases, the ZIF membranes are prepared without any seeding, support modification, or postsynthesis procedures, thereby simplifying the fabrication process and increasing the potential for larger‐scale membrane fabrication.