A Polystyrene Sulfonate Assisted Polyethylenimine Membrane for Stable, Scalable and Highly Effective CO2/N2 Separation

Greenhouse effect, largely caused by CO₂ release, has become a critical concern for global climate change. The post-combustion CO₂ capture is one of the major strategies to mitigate this issue. Membrane technology for carbon capture has drawn significant attention due to cost and energy efficiency and scalability. Many membranes for CO₂ capture are limited by the tradeoff between CO₂ permeance and CO₂/N₂ selectivity, poor long-term stability under actual operating condition (vacuum in permeate side). Facilitated CO₂ carriers within the membrane structure help to overcome the permeance-selectivity tradeoff. However, these carriers are often lost under operational conditions. Herein, we fabricate a polystyrene sulfonate (PSS) assisted polyethylenimine (PEI) membrane by simple membrane casting where the carriers (amine groups in PEI) are stabilized electrostatically, providing long-term stability (>50 h) under varying vacuum condition. The CO₂ permeance and selectivity could be tuned effectively by optimizing PEI loading. Our membrane shows a superior CO₂/N₂ separation performance with CO₂ permeance >1,000 GPU and CO₂/N₂ selectivity over 250. Scalability of our membrane was demonstrated by preparing membrane with area ~70 cm² while maintaining similar CO₂ separation performances.