Owing to their high surface areas, tunable pore dimensions, and adjustable surface functionality, metal-organic frameworks (MOFs) can offer advantages for a variety of gas storage and gas separation applications. In an effort to help curb greenhouse gas emissions from power plants, we are developing new MOFs for potential use as solid adsorbents in post- and pre-combustion CO2 capture, and for the separation of O2 from air, as required for oxy-fuel combustion. In particular, MOFs with diamine-functionalized surfaces have been demonstrated to provide high selectivities and capacities for the adsorption of CO2 over N2 under dry flue gas conditions. Thermogravimetric cycling and multicomponent adsorption measurements now further show that compounds of this type remain highly effective in the presence of water, while calorimetry data reveal a low regeneration energy compared to aqueous amine solutions. Most significantly, as determined by in situ nuclear magnetic resonance, infrared, x-ray absorption spectroscopy experiments, crystal structure determinations, and computational simulations, the unusual stepped CO2 adsorption isotherms exhibited by these materials arise from a unique cooperative insertion mechanism to form one-dimensional chains of metal-bound ammonium carbamates. A detailed understanding of this mechanism now enables us to design new materials for the low-energy separation of CO2 from a wide variety of key gas mixtures, including flue gases, air, biogas, and natural gas deposits.

Carbon dioxide capture in diamine-appended metal-organic frameworks

255th National Meeting (2018)

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