Responsive Porous Material for Discrimination and Selective Capture of Low-Concentration SO₂

The efficient removal of low-concentration SO 2 is of great significance but challenging due to the competitive adsorption of CO 2 . Herein, we report the efficient capture of low-concentration SO 2 with high selectivity over CO 2 by Mn(INA) 2 (INA = isonicotinate) with a designed pore structure. Notably, the channels of Mn(INA) 2 exhibit large cavities and narrow bottlenecks, leading to the exclusion of the larger molecules of N 2 and CH 4 . An interesting phenomenon was observed through single-crystal X-ray diffraction experiments where SO 2 “opened” the bottlenecks and entered the cavities via the rotation of the pyridine ring (12.2°) to enlarge the cavities to accommodate SO 2 molecules. These responsive properties of Mn(INA) 2 to SO 2 molecules afford high SO 2 /CO 2 separation selectivity. In addition, first-principles dispersion-corrected density functional theory (DFT-D) calculations elucidate that the high-density host–guest interactions including duple S δ+ ···O δ− electrostatic interactions, multiple H δ+ ···O δ− dipole–dipole interactions, and guest–guest interactions between SO 2 molecules are responsible for the sensitive response of the material toward low-concentration SO 2 (2000 ppm). The efficient SO 2 capture properties of Mn(INA) 2 are further demonstrated by the breakthrough experiments. Moreover, the material is stable and easy to scale up, which makes it promising for low-concentration SO 2 removal.