Develop Robust Metal-Organic Frameworks-based Adsorbents for Toxic and Corrosive Gases: Importance of Specific Binding Sites and Adsorption-Desorption Mechanism

Anthropogenic emissions of various toxic gases cause serious environmental problems and pose substantial health threats. Prominent examples of toxic gases include NO2, SO2, H2S, and NH3, generated from the burning of fossil fuels for energy production,various industrial processes, and agricultural activities. Mitigating the adverse impact of toxic gases requires effective gas treatment technologies – gas detection, removal, and conversion, which can be nicely enabled by selective gas adsorption in porous solids. Thekey to an effective gas adsorption operation is to have porous adsorbents capable of affording high selectivity, high capacity, high stability, and high regenerability. High adsorption selectivity and capacity assure effective enrichment of target toxic gases inadsorbents, while high stability and regenerability assure multiple reuses of adsorbent materials. However, few materials can simultaneously satisfy these four requirements because toxic gases are often of a highly reactive and corrosive nature. A dilemma exists in developing effective adsorbents – strong and specific binding sites, on one hand, are necessary to realize high adsorption selectivity and capacity, and on the other, are potentially detrimental to the stability and regenerability of adsorbents.  In this project, we aim to resolve this dilemma by addressing the following questions: 1)How to design and develop metal-organic frameworks (MOFs) adsorbents that combine robust framework and specific binding sites, such that the inert scaffold metal nodesassure overall high material stability and active non-scaffold transition metal centers impart highly specific adsorption; 2) How to fine-tune the adsorption selectivity, capacity, and regenerability by varying non-scaffold transition metal, scaffold metal node, and organic linker of porphyrin MOFs, based on our successful proof-of-concept study on NO2 adsorption; 3) How to elucidate the gas adsorption-desorption mechanism via a combined experimental and molecular simulation study to enable rational adsorbents design and controlled handling of toxic gases by adsorption. The research on fundamentals of gas adsorption serves as the cornerstone of a suite of gas technologies for the treatment of toxic and corrosive gases, including gas detection, gas removal/filtration, and (catalytic) gas conversion. Thus, the new knowledgegenerated in this proposal will be invaluable to advance each of these adsorption-based gas technologies, which will potentially bring considerable environmental, health, and economic benefits.