Simultaneous Boost of SF₆ Adsorption Capacity and Kinetics Through Isoreticular Functionalization of...

The capture of sulfur hexafluoride (SF₆), the most potent greenhouse gas, is of critical importance. Enhancement of dynamic SF₆ capture capacity presents significant challenges due to its chemical inertness and low concentration in industrial effluent streams. Herein, we demonstrate that the isoreticular functionalization of zinc-pyrazolate metal-organic frameworks (MOFs) enables simultaneous enhancement of both SF₆ adsorption capacity and uptake kinetics. Through replacement of benzene with pyridine in the ligand, BUT-125 (BUT: Beijing University of Technology) achieves a record-high SF₆ adsorption capacity of 3.57 mmol cm^-3 at 0.1 bar and 298 K, representing a 27% improvement over its structural analogue Zn-DPB (DPB: 1,3-di(pyrazolate-4-yl)benzene). Density functional theory (DFT) calculations reveal that pyridine functionalization increases the positive charge density on hydrogen atoms within molecular trap sites, strengthening C─H···F interactions with SF₆ molecules. Remarkably, BUT-125 also exhibits outstanding adsorption kinetics, that combined with high equilibrium uptake, leads to an exceptional dynamic SF₆ capture capacity of 3.42 mmol cm^-3 from the SF₆/N₂ (10/90) mixture, surpassing reported porous sorbents.