Exceptional SF ₆ /N ₂ Separation of Metal–Organic Frameworks by Overcoming the Capacity‐Selectivity Trade‐Off via Ligand Engineering

Abstract The effective capture of sulfur hexafluoride (SF ₆ ) is crucial from both economic and environmental viewpoints. However, the investigation of low‐energy and sustainable methods for separating SF ₆ from the SF ₆ /N ₂ mixture remains challenging. Herein, a ligand engineering strategy is employed to optimize the metal–organic framework (MOF) adsorbent for effective separation of SF ₆ and N ₂ . By utilizing the isoreticular chemistry with structurally similar tetracarboxylic acid ligands, a series of Al‐MOFs is constructed, enabling systematic and precise pore size optimization and surface functionalization to enhance SF ₆ binding affinity. Remarkably, the compound 4 , based on 2,3,5,6‐tetrakis(4‐carboxyphenyl)pyrazine ligand, is screened to exhibit both high SF ₆ uptake at low pressure (55 cm ³ g ⁻¹ at 10 kPa and 84 cm ³ g ⁻¹ at 100 kPa, 298 K) and high SF ₆ /N ₂ selectivity of (512 for 10/90 mixture), which surpasses most reported MOFs. Furthermore, breakthrough experiments demonstrate that these Al‐MOFs can recover high‐purity SF ₆ from low‐concentration (10%) SF ₆ /N ₂ mixture under high‐humidity conditions, with exceptional stability over multiple cycles. Theoretical calculations reveal the supramolecular interactions between SF ₆ and the framework, elucidating the mechanism behind the superior performance of these materials. This work highlights the potential of pore engineering in MOFs to overcome the selectivity‐uptake trade‐off, offering a sustainable solution for SF ₆ management.