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CO2 Adsorption and Separation in Covalent Organic Frameworks with Interlayer Slipping


The energetic stability of layered covalent organic frameworks (COFs) in slipped structures and the experimental control of interlayer slipping (Nat. Commun. 2014, 5, 4503) suggest that the interlayer slipping could be used as a design parameter to enhance the gas adsorption and separation properties of COFs. In this work, we have systematically studied the effect of interlayer slipping on CO2 adsorption and CO2/N2 separation in microporous TpPa1, and mesoporous TpBD and PI-COFs using quantum mechanical and grand canonical Monte Carlo simulations. We found that the slipping affects the number of preferred CO2 adsorption regions and corresponding adsorption energies, resulting in a drastic variation in the adsorption uptake. Our detailed analysis of heat of adsorption, density distribution and energy landscape reveals that the effect of slipping on CO2 uptake is non-monotonous. We explain this behavior using a simplified model that also provides an optimal range of slipping distance to increase the gas storage performance of COFs. Our results show that the optimized slipped COF structures have approximately three times higher CO2 working capacity and CO2:N2 selectivity as compared to eclipsed structure. A highest CO2 working capacity of 5.8 mol kg-1 and CO2:N2 separation selectivity of 197 (at 1 bar and 298 K) was observed for slipped PI-COF-2 and TpBD COFs, respectively, higher than any other COFs reported till date. The molecular insight presented here is qualitatively applicable to other similar slipped COFs and is useful for the development of COFs for enhanced gas storage and separation applications.

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Publication details

The article was received on 13 Sep 2017, accepted on 13 Oct 2017 and first published on 13 Oct 2017

Article type: Paper
DOI: 10.1039/C7CE01647F
Citation: CrystEngComm, 2017, Accepted Manuscript
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    CO2 Adsorption and Separation in Covalent Organic Frameworks with Interlayer Slipping

    A. Sharma, A. Malani, N. Medhekar and R. Babarao, CrystEngComm, 2017, Accepted Manuscript , DOI: 10.1039/C7CE01647F

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