Ultrahigh and Selective SO2 Uptake in Inorganic Anion‐Pillared Hybrid Porous Materials

Abstract

The efficient capture of SO 2 is of great significance in gas‐purification processes including flue‐gas desulfurization and natural‐gas purification, but the design of porous materials with high adsorption capacity and selectivity of SO 2 remains very challenging. Herein, the selective recognition and dense packing of SO 2 clusters through multiple synergistic host–guest and guest–guest interactions by controlling the pore chemistry and size in inorganic anion (SiF 62−, SIFSIX) pillared metal–organic frameworks is reported. The binding sites of anions and aromatic rings in SIFSIX materials grasp every atom of SO 2 firmly via S δ+···F δ− electrostatic interactions and O δ−···H δ+ dipole–dipole interactions, while the guest–guest interactions between SO 2 molecules further promote gas trapping within the pore space, which is elucidated by first‐principles density functional theory calculations and powder X‐ray diffraction experiments. These interactions afford new benchmarks for the highly efficient removal of SO 2 from other gases, even if at a very low SO 2 concentration. Exceptionally high SO 2 capacity of 11.01 mmol g−1 is achieved at atmosphere pressure by SIFSIX‐1‐Cu, and unprecedented low‐pressure SO 2 capacity is obtained in SIFSIX‐2‐Cu‐i (4.16 mmol g−1 SO 2 at 0.01 bar and 2.31 mmol g−1 at 0.002 bar). More importantly, record SO 2/CO 2 selectivity (86–89) and excellent SO 2/N 2 selectivity (1285–3145) are also achieved. Experimental breakthrough curves further demonstrate the excellent performance of these hybrid porous materials in removing low‐concentration SO 2.