Triple-ligand zeolitic imidazolate frameworks for highly CO2 selective mixed matrix membranes

Abstract

• A series of triple ligand-coordinated ZIF-8s (TAZIF-8s) were successfully prepared. • The TAZIF-8s enhanced chemical interaction and molecular sieving ability toward CO 2 . • A high dispersibility of TAZIF-8s enabled high TAZIF-8 loading (40 wt%) mixed matrix membranes (MMMs). • TAZIF-8 MMMs effectively suppressed both the physical aging and CO 2 -induced plasticization. • High CO 2 separation performance of TAZIF-8 MMMs was retained even after water vapor exposure. Here, we report a new class of highly CO 2 selective ZIF nanoparticles, TAZIF-8, consisting of zinc metals and triple ligands, including 2-methylimidazole (MIm), tributylamine (TBA), and 3-amino-1,2,4-triazole (Atz). The Zn-MIm coordination retains an open porous sodalite topology, while the Zn-TBA analogue contributes to high processability. Lastly, the Zn-Atz coordination enables favorable CO 2 permeation via a combination of enhanced size discrimination and specific chemical interactions. A high loading 6FDA-DAM/TAZIF-8 (40 wt%) mixed matrix membrane consequently exhibits an almost threefold increase in CO 2 permeability and a twofold increase in CO 2 selectivity over other light gases (N 2 , CO, or CH 4 ) compared to high performance 6FDA-DAM membrane. Furthermore, it maintains excellent CO 2 separation performance over 90 days and even after exposure to water vapor. Our multiple hybrid modification technique enables the fine-tuning of the physical structure and textural properties of ZIF for enhanced CO 2 separation performance.