Metal Organic Frameworks and Microporous Polymers as Carbon Capture Materials: Effects of Functionality and Alkali Metal Cation Incorporation

The removal of carbon dioxide from the flue gas of coal fired power plants and from natural gas streams represents a monumental challenge that must be overcome in order to satisfy the world's energy needs without catastrophically changing the global climate. Metal organic frameworks (MOFs) and porous organic polymers (POPs) represent two classes of materials that could provide solutions to multiple gas separation applications, including selective carbon dioxide capture. Materials that selectively bind CO2 with high capacity are a necessity for any carbon capture and sequestration (CCS) system to be viable. Both MOFs and POPs possess ultra-high surface area. The high surface areas stem directly from the microporous nature of the materials. The chemical environment of these micropores can be altered to enhance selective attraction to certain gas species. The focus of this research is to discover what changes in the chemical environment of the pores lead to enhanced selective CO 2 uptake.;Several new MOF and POP structures have been designed and synthesized. These new structures and some previously known structures are chemically modified. Modification methods include synthesis of ligands with nitro- or amino- functionality, post-synthesis incorporation of lithium cations, and thermal treatment. Amine functionalized pores are found to exhibit a slightly higher binding energy towards CO2 than an isostructural non-functionalized framework. The presence of lithium cations is found to enhance the selective adsorption of CO2 versus methane. The mechanism by which the enhancement takes place depends upon the method used to incorporate the lithium cations, metal reduction or cation exchange. Thermal treatment of highly stable POPs is found to increase apparent surface area and uptake of CO2.