Single-Crystal COF Membranes Hit 74,800 Barrer CO2 Permeability, Moving Cheaper Carbon Capture Closer

Researchers at Tianjin University, EPFL, and USC report a new mixed-matrix membrane for post-combustion carbon capture. By embedding single-crystal covalent organic frameworks (COFs) into a polymer at up to 75.5 percent loading by volume, they achieved a CO2 permeability of 74,800 Barrer while keeping CO2/N2 selectivity near 20. That combination pushes the material well past the conventional permeability-selectivity trade-off that limits polymer membranes. The work appears in Nature Energy. Unlike earlier mixed-matrix membranes that lose performance at high filler fractions, the team used a weak-interaction inlaying strategy to keep the COF crystals evenly dispersed. The all-organic membrane is solution processable, so it fits existing fabrication routes. A six-month ageing test with polyimide-based membranes retained about 85 percent of initial permeability, a sign that the crystalline filler helps slow the physical ageing that usually degrades polymer membranes. Lab results still need to survive pilot testing on real flue gas, including humidity, sulfur, and temperature swings. But if the material scales, it could reduce the membrane area and energy demand of capture plants, which would lower the cost of CCS projects. The full paper is available at DOI 10.1038/s41560-026-02149-9.