Metal-Organic Frameworks with Potential Application for SO2 Separation and Flue Gas Desulfurization

Sulfur dioxide (SO2) is an acidic and toxic gas and its emission from utilizing energy from fossil fuels or in industrial processes harms human health and environment. Therefore, it is of great interest to find new materials for SO2 sorption to improve classic flue gas desulfurization. In this work, we present SO2 sorption studies for the three different metal-organic frameworks MOF-177, NH2-MIL-125(Ti), and MIL-160. MOF-177 revealed a new record high SO2 uptake (25.7 mmol-g(-1) at 293 K and 1 bar). Both NH2-MIL-125(Ti) and MIL-160 show particular high SO2 uptakes at low pressures (p < 0.01 bar) and thus are interesting candidates for the removal of remaining SO2 traces below 500 ppm from flue gas mixtures. The aluminum furandicarboxylate MOF MIL-160 is the most promising material, especially under application-orientated conditions, and features excellent ideal adsorbed solution theory selectivities (124-128 at 293 K, 1 bar; 79-95 at 353 K, 1 bar) and breakthrough performance with high onset time, combined with high stability under both humid and dry SO2 exposure. The outstanding sorption capability of MIL-160 could be explained by DFT simulation calculations and matching heat of adsorption for the binding sites O-furan center dot center dot center dot S-SO2 and OHAI-chain center dot center dot center dot O-SO2 (both similar to 40 kJ.mol(-1)) and O-furan/carboxylate center dot center dot center dot S-SO2 (similar to 55-60 kJ.mol(-1)).