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

Emissions of SO 2 from flue gas and marine transport have detrimental impacts on the environment and human health, but SO 2 is also an important industrial feedstock if it can be recovered, stored and transported efficiently. Here we report the exceptional adsorption and separation of SO 2 in a porous material, [Cu 2 (L)] (H 4 L = 4′,4‴-(pyridine-3,5-diyl)bis([1,1′-biphenyl]-3,5-dicarboxylic acid)), MFM-170. MFM-170 exhibits fully reversible SO 2 uptake of 17.5 mmol g −1 at 298 K and 1.0 bar, and the SO 2 binding domains for trapped molecules within MFM-170 have been determined. We report the reversible coordination of SO 2 to open Cu( ii ) sites, which contributes to excellent adsorption thermodynamics and selectivities for SO 2 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 SO 2 from simulated flue gas mixtures, as confirmed by breakthrough experiments. Metal–organic framework capture materials could reduce the environmental impact of SO 2 emissions but can have limited stability and poor reversibility. Here, a metal–organic framework with open Cu( ii ) sites with fully reversible SO 2 uptake of 17.5 mmol g −1 under ambient conditions is reported.