Synergistic Pore Microenvironment Engineering in Zinc Metal–Organic Frameworks for High SF ₆ /N ₂ Selectivity and Humidity‐Resistant Trace SF ₆ Capture

Abstract

ABSTRACT Sulfur hexafluoride (SF 6 ) is a potent greenhouse gas widely used in electrical insulation. Although the size difference between SF 6 and N 2 enables separation in principle, achieving high SF 6 selectivity at trace concentrations, large adsorption capacity, and long‐term stability remains a formidable challenge. Herein, we report a family of new zinc‐based metal‐organic frameworks ( Zn‐tcpb , Zn‐tcpb‐bim , Zn‐tppb‐bim ) with systematically tunable pore sizes and electrostatic microenvironments. By integrating a mixed‐ligand strategy (tetracarboxylic acids plus 2,2'‐biimidazole) with pore functionalization, we achieve synergistic control over adsorption and separation properties. Among them, Zn‐tppb‐bim— featuring electron‐withdrawing pyrazine rings—exhibits a remarkable low‐pressure SF 6 uptake of 3.06 mmol/g at 0.1 bar, and an excellent SF 6 /N 2 IAST selectivity of 606 (1:9, 1 bar), achieving a balance between uptake and selectivity. Theoretical calculations reveal that the N‐heterocyclic units in Zn‐tppb‐bim generate a stronger positive framework charge, enhancing C─H···F interactions with SF 6 . Dynamic breakthrough experiments confirm complete separation of SF 6 /N 2 mixtures. Remarkably, the materials retain full separation performance even at 80% relative humidity. This work demonstrates a viable and generalizable design strategy that synergistically optimizes adsorption capacity, selectivity, and humidity resistance, providing a rare example of metal–organic framework that are both highly efficient and stable under practical conditions.