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Modeling of Adsorption of Molecules in Pristine and Defective UiO-66

Shukla, Priyanka Bholanath (2021) Modeling of Adsorption of Molecules in Pristine and Defective UiO-66. Master's Thesis, University of Pittsburgh. (Unpublished)

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Abstract

Metal-organic frameworks are nanoporous materials that are used for various applications such as gas adsorption, storage, and separations. Our work focuses mainly on the UiO family of Zr-based MOFs, which may be used to capture and destroy chemical warfare agents (CWA) and their simulants. We have studied the adsorption of molecules such as nitrogen, isopropanol, and acetone in UiO-66 with different framework and molecule potentials in order to understand the basic interactions and adsorption mechanism.

The fully coordinated dense structure of UiO-66 has very small pore windows that limit access of larger molecules and thus decreases the adsorption capacity for CWAs. Thus, we have created missing linker defects in Pristine UiO-66 in order to increase accessibility to the pores. Defects may be created experimentally by adding modulators such as acetic acid, formic acid, hydrochloric acid, and other solvents while synthesizing the UiO-66 material where they compete with the organic linkers to form bonds with the Zr6 metal clusters. We have studied the adsorption of molecules in defective UiO-66 with different capping groups such as hydroxide, formate, and acetate and increasing the level of defects. We have studied 4%, 8%, 17%, and 33% missing linker defects. We observe that the saturation uptake increases with the increase in the defect level.

The modeling was done by holding the framework structure rigid in-order to increase the computational efficiency. However, the intrinsic framework flexibility may have a significant impact on the adsorption. To further explore this phenomenon, we have studied the impact of intrinsic framework flexibility on the adsorption of acetone and nitrogen in pristine UiO-66. The modeling was done by performing GCMC simulations on structures generated from NVT-MD snapshots of the empty and finite loaded UiO-66 framework. The results show that introducing framework flexibility increases the adsorption of acetone for both the empty framework and finite loading acetone framework but does not accommodate more nitrogen molecules. This suggests that accurate isotherms require NVT-MD simulations with finite loading of the desired molecule in the framework, followed by modeling of the adsorption isotherm.


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Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Shukla, Priyanka Bholanathpbs13@pitt.edupbs130000-0002-6653-0552
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Thesis AdvisorJohnson, JKkarlj@pitt.edukarlj
Committee ChairJohnson, JKkarlj@pitt.edukarlj
Committee MemberWilmer, Christopher Ewilmer@pitt.eduWilmer
Committee MemberRosi, Nathaniel Lnrosi@pitt.edunrosi
Date: 13 June 2021
Date Type: Publication
Defense Date: 19 March 2021
Approval Date: 13 June 2021
Submission Date: 4 April 2021
Access Restriction: 1 year -- Restrict access to University of Pittsburgh for a period of 1 year.
Number of Pages: 73
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Chemical Engineering
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: Adsorption, RASPA, isotherms, UiO-66, flexible
Date Deposited: 13 Jun 2021 17:30
Last Modified: 13 Jun 2021 17:30
URI: http://d-scholarship.pitt.edu/id/eprint/40509

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