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 (S^δ+···O^δ- interactions) and aromatic linkers in the pore walls (H^δ+···O^δ- 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.