(531c) Hydrogen-Bonded Polyimide/Metal-Organic Framework Hybrid Membranes for Ultra-Fast Separations of Multiple Gas Pairs

Membranes can effectively reduce the enormous amount of energyrequired for gas separations, compared to conventional separation processes, such as cryogenic distillation. Currently, polymers dominate gas separation membrane markets due to their appealing manufacturability and performance. However, polymeric membranes suffer from the productivity-selectivity tradeoff, i. e., the Robeson upper bound. To overcome this challenge, growing attention has been shifting towards hybrid materials synergistically utilizing advantages of each component in the hybrid membranes, i.e., easy processing of polymers and molecular sieving of fillers, such as metal-organic framework (MOFs). However, only a few MOF-based hybrid membranes perform above current Robeson upper bounds, predominantly relying upon rigid Polymers of Intrinsic Microporosity or aggressive thermal annealing as high as 240 ^oC, adding complications for scaling-up. Moreover, most hybrid membranes are specialized for a particular gas pair (e.g. CO₂/N₂), lacking a general approach to separating multi-component gas mixtures.

This work demonstrates new classes of polyimide/MOFs hybrid membranes residing above current Robeson upper bounds via a generalizable approach. The hydrophilic amino (-NH₂) groups in MOFsintensively interact with carboxylic moieties in a 6FDA-based polyimide via hydrogen bonds to foster a firm interphase adhesion. The polyimide/MOFshybrid membranes demonstrate a CO₂and H₂permeability of 2494 and 2932 Barrers, respectively, with a CO₂/CH₄, H₂/CH₄and H₂/N₂selectivity of 29.3, 34.4, and 23.8 respectively, surpassing current Robeson upper bounds considerable. The permeability was enhanced by record-high 16 times comparing with the neat polymer.­ With a processing temperature as low as 80 ^oC and performance continuously exceeding the upper bounds for over 5300 hr, the membrane is readily compatible with state-of-the-art membrane manufacture processes.