(350a) Mixed-Metal Metal-Organic Frameworks for Selective Adsorption of Sulfur Dioxide

Both natural gas and biogas have an increasing presence in the energy sector because of their relatively low carbon-intensity. To isolate the methane fuel, hydrogen sulfide (along with other impurities), must be removed to maximize heat content. Additionally, sulfur dioxide present in flue gas streams must be removed to prevent the formation of acid rain. Selective adsorption of sulfur gases presents itself as an energy-efficient separation approach. Because of their high degree of tunability, metal-organic frameworks (MOFs) are promising adsorbent materials for applications with varying process stream concentrations. One approach to tuning MOF properties is by incorporating multiple metals to serve as framework nodes; the introduction of additional metals has the potential to enhance adsorption capacity and stability in humid/acidic environments.

This work seeks to explore the relationship between MOF metal composition and suitability for SO₂/CO₂ separation. The widely used MOF-74(Mg) was used as a parent material, and varying amounts of Cu, Co, and Ni were incorporated into the framework structure. Single component adsorption isotherms of CO₂ and SO₂, as well as multicomponent SO₂/CO₂ breakthroughs, were conducted. The resulting experimental adsorptive capacity and mixture selectivity values were calculated and compared to monometallic MOF-74. Additionally, the thermal and mechanical stabilities of the bimetallic MOFs were compared to their parent materials.