Highly Selective and Reversible Sulfur Dioxide Adsorption on a Microporous Metal–Organic Framework via Polar Sites

It is very challenging to achieve efficient and deep desulfurization, especially in flue gases with an extremely low SO2 concentration. Herein, we report a microporous metal–organic framework (ELM-12) with specific polar sites and proper pore size for the highly efficient SO2 removal from flue gas and other SO2-containing gases. A high SO2 capacity of 61.2 cm3·g–1 combined with exceptionally outstanding selectivity of SO2/CO2 (30), SO2/CH4 (871), and SO2/N2 (4064) under ambient conditions (i.e., 10:90 mixture at 298 K and 1 bar) was achieved. Notably, the SO2/N2 selectivity is unprecedented among ever reported values of porous materials. Moreover, the dispersion-corrected density functional theory calculations illustrated the superior SO2 capture ability and selectivity arise from the high-density SO2 binding sites of the CF3SO3– group in the pore cavity (Sδ+···Oδ− interactions) and aromatic linkers in the pore walls (Hδ+···Oδ− interactions). Dynamic breakthrough experiments confirm the regeneration stability and excellent separation performance. Furthermore, ELM-12 is also stable after exposure to SO2, water vapor, and organic solvents.