(693a) Amorphous Polymofs Membranes for Pre-Combustion CO2 Capture

Membrane technology with superior H₂/CO₂ separation properties has gained significant attention for pre-combustion CO₂ capture. Advanced membrane materials with both high H₂ permeability and H₂/CO₂ selectivity are needed for gas separation to reduce the capital and energy cost. Herein, we demonstrated amorphous poly(metal organic frameworks) (aPolyMOFs) derived from metal ion-coordinated polybenzimidazole (PBI), achieving superior H₂/CO₂ separation properties. Metal ions, including Fe³⁺, Zn²⁺, and Co²⁺, can coordinate with imidazole rings on PBI in the presence of free imidazole ligands, forming aPMOF structures containing 1.2−2.8 wt% metal ion and 3.2−7.4 wt% imidazole. The derived films exhibit increased densities and d-spacings. Increasing the metal ion content in aPMOF increased the gel content and density, leading to increased size-sieving ability and H₂/CO₂ selectivity. While further increase of metal ion content leaded to sharp peaks on the wide-angle X-rau diffraction patterns, impling the formation of crystalline MOF structures. For example, compare to pristine PBI film with H₂/CO₂ selectivity of 11 and H₂ permeability of 1.7 Barrer at 35 ^oC, a Fe³⁺-containing aPMOF film exhibits a H₂/CO₂ selectivity of 47, companied by an H₂ permeability of 2.5 Barrer. Particularly, the film demonstrated stable mixed-gas H₂/CO₂ separation performance under simulated conditions for pre-combustion CO₂ capture, achieving a mixed-gas H₂ permeability of 3.4 Barrer and an H₂/CO₂ selectivity of 26 at 60 ^oC. This performance significantly exceeds the upper bound and most state-of-the-art polymeric materials. Our findings highlight the substantial potential of aPMOF membranes for gas separation applications.