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Thesis (5).pdf (7.65 MB)
ETD Abstract Container
Abstract Header
Infrared and Thermal-Desorption Spectroscopy of H
2
and D
2
in Metal Organic Frameworks
Author Info
Shinbrough, Kai
ORCID® Identifier
http://orcid.org/0000-0002-4277-0324
Permalink:
http://rave.ohiolink.edu/etdc/view?acc_num=oberlin1495632169708899
Abstract Details
Year and Degree
2017, BA, Oberlin College, Physics and Astronomy.
Abstract
In this thesis we provide an introduction to the use of Metal-Organic Frameworks (MOFs) for hydrogen storage and for the separation of hydrogen isotopologues, H
2
and D
2
. MOFs are a class of materials comprised of `building-block’ metal-oxide clusters connected by organic ligands, which have the capacity to adsorb molecules such as hydrogen through weak, physisorptive mechanisms. We provide some background on the quantum mechanical structure of hydrogen isotopologues, the structure of a few state-of-the-art MOFs, the quantum mechanics of infrared spectroscopy, and the desorption dynamics of adsorbates generally. We provide a description of the experimental apparatus and procedure used in this work to acquire thermal desorption (TD) and simultaneous,
in situ
infrared (IR) spectra. Notably, this apparatus makes use of a pressure gauge to record TD spectra—to the best of the author’s knowledge, this is the first time such an apparatus has been created and shown to produce reproducible, physically-informative TD spectra. We demonstrate the potential of this novel spectroscopic technique on three MOFs, as we report their respective TDS and IR signatures. The agreement between our TDS and IR techniques is remarkable, as is the amount of information apparent in the TD spectra, and the agreement of our TD spectra with those in the literature. With our simple technique we are able to clearly distinguish the TD spectra of H
2
and D
2
, allowing for the evaluation of MOFs with respect to their isotopologue separating ability. In addition to a proof of concept as to the proficiency of the experimental apparatus, this work presents two main findings: that the desorption of hydrogen isotopologues from MOFs does not follow the coverage-independent Polanyi-Wigner equation, and that stronger binding MOFs exhibit diminishing returns with respect to their ability to separate hydrogen isotopologues via temperature programming. As we argue on several occasions in this thesis, the TD spectra of hydrogen desorbing from the MOFs examined with our technique do not obey the coverage-independent Polanyi-Wigner equation. This is foremost demonstrated by the poor
ab initio
fits of our spectra to the equation. This result is also corroborated by the coverage dependence of the TD spectra of Co-MOF-74 (dobdc), however, and further by the ramp rate dependence of these spectra. In demonstrating this result, we advise against the use of the coverage-independent Polanyi-Wigner equation—and analysis techniques based off of it—when considering the desorption of hydrogen from MOFs. As these techniques have begun to feature prominently in the literature, this result proves exceedingly pertinent. We arrive at the latter conclusion by examining the MOFs reported on as a group, and examining the separation of H
2
and D
2
TD peaks as a function of MOF binding energy. We conclude through experimental as well as through computational techniques that the prospect of temperature-programmed separation through total desorption of H
2
and total adsorption of D
2
is exceedingly bleak. This surprising result rules out the most straightforward use of MOFs for hydrogen isotopologue separation, what we name Zero Point Energy Separation (ZPES) at a single site. As the field surrounding MOFs tacitly assumes this as a promising possibility, again this result proves exceedingly pertinent. The prospect of more imaginative uses of MOFs for temperature-programmed isotopologue separation remains open, as does the possibility of isotopologue separation through other mechanisms involving MOFs.
Committee
Stephen FitzGerald (Advisor)
Pages
119 p.
Subject Headings
Materials Science
;
Physical Chemistry
;
Physics
;
Quantum Physics
Keywords
MOFs
;
Metal-Organic Frameworks
;
Porous materials
;
H2-D2 separation
;
hydrogen separation
;
deuterium separation
;
temperature-programmed desorption
;
thermal desorption spectroscopy
;
infrared spectroscopy
;
trapped hydrogen
;
quantum sieving
Recommended Citations
Refworks
EndNote
RIS
Mendeley
Citations
Shinbrough, K. (2017).
Infrared and Thermal-Desorption Spectroscopy of H
2
and D
2
in Metal Organic Frameworks
[Undergraduate thesis, Oberlin College]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=oberlin1495632169708899
APA Style (7th edition)
Shinbrough, Kai.
Infrared and Thermal-Desorption Spectroscopy of H
2
and D
2
in Metal Organic Frameworks.
2017. Oberlin College, Undergraduate thesis.
OhioLINK Electronic Theses and Dissertations Center
, http://rave.ohiolink.edu/etdc/view?acc_num=oberlin1495632169708899.
MLA Style (8th edition)
Shinbrough, Kai. "Infrared and Thermal-Desorption Spectroscopy of H
2
and D
2
in Metal Organic Frameworks." Undergraduate thesis, Oberlin College, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=oberlin1495632169708899
Chicago Manual of Style (17th edition)
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Document number:
oberlin1495632169708899
Download Count:
1,227
Copyright Info
© 2017, all rights reserved.
This open access ETD is published by Oberlin College Honors Theses and OhioLINK.