Selective Gas Permeation in Mixed Matrix Membranes Accelerated by Hollow Ionic Covalent Organic Polymers

Mixed matrix membranes (MMMs) have gained great attention for the efficient CO ₂ removal from raw nature gas or biogas (CO ₂ /CH ₄ separation) and flue gas (CO ₂ /N ₂ separation). Nevertheless, the development of high-performance MMMs for industrial applications is largely limited by the lack of suitable porous fillers. Herein, a novel ionic covalent organic polymer (ICOP-1) consisting of gas selective pores and hollow cavities is facilely fabricated using a metal triflate catalyzed condensation reaction. Considering its unique structural properties, ICOP-1 is explored as a novel filler to enhance the gas separation properties of polysulfone (PSf) membranes. Defect-free MMMs are successfully prepared owing to the high polymer-filler affinity originating from the organic nature of these two phases. Besides, the large cavities and size-selective pores of ICOP-1 lead to a simultaneous increase in membrane CO ₂ permeability and CO ₂ /CH ₄ , CO ₂ /N ₂ selectivities. With the addition of only 0.5 wt % of ICOP-1 fillers, the as-prepared MMM demonstrates the optimal gas separation performance with a CO ₂ /CH ₄ selectivity of 39.7 (at a CO ₂ permeability of 6.19 Barrer) and a CO ₂ /N ₂ selectivity of 36.7 (at a CO ₂ permeability of 6.85 Barrer), opening new opportunities in membrane-based industrial CO ₂ capture applications.