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

Abstract

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···S_SO2 and OH_Al-chain···O_SO2 (both ∼40 kJ·mol^-1) and O_{furan/carboxylate}···S_SO2 (∼55-60 kJ·mol^-1).

Keywords: DFT simulation; breakthrough; flue gas desulfurization; gas selectivity; metal−organic framework; sulfur dioxide sorption.