High-performance ZIF-302 mixed-matrix membranes for efficient CO₂ capture

High-performance mixed matrix membranes (MMMs) were developed to assist in controlling global warming by capturing carbon dioxide (CO₂) from moist flue gas. However, the separation performance of MMMs has always been limited by gas permeability and long-term operating stability under humid conditions. ZIF-302 is a novel chabazite (CHA) topology structure with hydrophobic ligand. Herein, uniform ZIF-302 nanocrystals were doped into the P84 polymer matrix to synthesize different content of defect-free ZIF-302/P84 MMMs for CO₂/N₂ separation. A significant combination of gas permeability and separation factors was found in MMMs with a ZIF-302 packing load of 30 wt%. The gas permeability of CO₂ and the separation factor of CO₂/N₂ were significantly increased to 5.2 Barrers and 46, respectively, which breaks the trade-off between permeability and selectivity of the polymer membrane. In addition, the long-term operation stability showed that the separation performance of ZIF-302/P84 MMMs for CO₂/N₂ was maintained more than 30 h at 3 bar and 60 °C. The main characteristics of the MMMs prepared in this paper include the combination of favorable structural stability under humid conditions and unaffected CO₂/N₂ gas separation performance.