(278c) Supramolecular Polymer Networks of Ion-Coordinated Polybenzimidazole for High-Temperature H2/CO2 Separation

Membrane technology with superior H₂/CO₂ separation properties at high temperatures 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 facilely novel thermally-stable supramolecular polymer networks (SPNs) comprising of metal salt (palladium trifluoroacetate and nickel trifluoroacetate: Pd(CF₃COO)₂ and Ni(CF₃COO)₂) and polybenzimidazole (PBI) for H₂/CO₂ separation at high temperatures. With metal ions coordinating imidazole rings on PBI chains and trifluoroacetate anions unwinding the chain packing, the supramolecular network formed a bottleneck/microcavity bimodal pore architecture, leading to simultaneously increased H₂ permeability and H₂/CO₂ selectivity. Particularly, PBI-Ni(CF₃COO)₂ supramolecular network with a salt doping level of 0.17 displayed H₂ permeability of 62 Barrer at 150 ℃, increased by ~ 100 % from pristine PBI with H₂/CO₂ selectivity increasing from 10 to 15. Those supramolecular network films also exhibited improved mechanical properties and stable mixed-gas H₂/CO₂ separation performance at high temperatures. This study unveiled a facile approach to design membrane materials with bottleneck/microcavity bimodal pore architectures, thereby achieving both high gas permeability and selectivity.