Reversible coordinative binding and separation of sulfur dioxide in a robust metal–organic framework with open copper sites

Emissions of SO2 from flue gas and marine transport have detrimental impacts on the environment and human health, but SO2 is also an important industrial feedstock if it can be recovered, stored and transported efficiently. Here we report the exceptional adsorption and separation of SO2 in a porous material, [Cu2(L)] (H4L = 4',4‴-(pyridine-3,5-diyl)bis([1,1'-biphenyl]-3,5-dicarboxylic acid)), MFM-170. MFM-170 exhibits fully reversible SO2 uptake of 17.5 mmol g-1 at 298 K and 1.0 bar, and the SO2 binding domains for trapped molecules within MFM-170 have been determined. We report the reversible coordination of SO2 to open Cu(II) sites, which contributes to excellent adsorption thermodynamics and selectivities for SO2 binding and facile regeneration of MFM-170 after desorption. MFM-170 is stable to water, acid and base and shows great promise for the dynamic separation of SO2 from simulated flue gas mixtures, as confirmed by breakthrough experiments.