(682d) Atomistic Understandings of the CO2 Uptake Difference in Photo Responsive Metal-Organic Frameworks

Authors: 
Yang, C. T. - Presenter, The Ohio State Universtity
Lin, L. C., The Ohio State University
Global climate change owing to anthropogenic CO2 emissions has prompted nationwide actions from academia to industries to look for strategies to reduce atmospheric CO2 concentrations. To this end, carbon capture and sequestration has been regarded as a promising technology to substantially reduce the CO2 emission from power plants, one of the largest point emission sources. Conventionally, amine absorbers are used to separate CO2, but the energy requirement of a plant can be increased by 25-40%.1-2 Recently, metal-organic frameworks (MOFs) have drawn significant attention as a promising alternative because of their desirable properties (e.g., large surface area, adjustable chemical functionality, high selectivity of CO2 over N2, etc.).3 Moreover, experimentists have further developed photo-switchable (azobenzene functionalized) MOFs whose affinity for CO2 adsorption can be modified by light irradiation (transformation from trans to cis configurations), resulting in a CO2 uptake difference of more than 50%.4 This has potentially led to a more energy-efficient CO2 capture process as compared to traditional materials. Despite the success, the atomistic understandings of the root cause behind the observed uptake difference remain limited. In this study, by using state-of-the-art molecular simulations and density functional theory calculations, we investigate the adsorption mechanisms in azobenzene functionalized MOF-5 (azo-MOF5) that leads to the experimentally observed CO2 uptake difference between cis and trans configurations. The free energy landscape of CO2 molecules as well as minimum energy configurations will be computed and analyzed in detail to identify preferential adsorption sites in azo-MOF5 for CO2. The effect of the azobenzene density on the uptake difference will also be studied. The outcomes of this study are anticipated to provide insights into the design of this stimulus-responsive MOFs to push the development of CO2 capture and sequestration.

Reference

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