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Thesis Format

Integrated Article

Degree

Master of Science

Program

Chemistry

Supervisor

Huang, Yining

Abstract

Metal-organic frameworks (MOFs) are a class of hybrid organic-inorganic microporous materials with lots of significant applications including gas capture and storage, gas separation, batteries, catalysis, ion exchange and drug delivery. MOFs based on s-block metals are important due to their many practical applications. These MOFs are also very interesting because the s-block MOFs often exhibit unpredictable behavior of coordination. In this thesis, the structures of six s-block metal (Li, Na, Cs, Mg, Ca, Sr) based MOFs involving V-shaped link, 4, 4′- sulfonyldibenzoate (SDB) are characterized by various techniques including, powder X-ray diffraction, TGA and solid-state NMR spectroscopy. 13C CPMAS NMR was used to probe the local structure around SDB linkers. 7Li, 23Na, 133Cs, and 25Mg SSNMR were utilized to directly characterize the metal center surroundings. Explicitly, variable temperature (VT) 13C SSNMR spectroscopy is used to investigate the behavior of 13CO2 in four selected MOFs with porous channels. The analysis of 13C static spectra reveals that CO2 molecules undergo localized wobbling and non-localized hopping within these MOFs. Additionally, all these s-block MOFs based on SDB share the common adsorption site (π-pocket of SDB ligands). Moreover, another novel MOF, UTSA-280, with Ca center and C4O4 ligands is also studied. Based on its rigid channel size, UTSA-280 shows a high separation performance of CO2 from CH4 and C2H4 from C2H6 under ambient condition. In this thesis, the behaviors of 13CO2 and C2D2 within UTSA-280 are investigated via VT 13C wide-line SSNMR experiments and VT 2H wide-line SSNMR experiments, respectively. The results show a tight guest-host interactions. Meanwhile, with the same ligands as UTSA-280, MOF (Zn(bipy)(C4O4)(H2O)2) is briefly studied as well.

Summary for Lay Audience

Metal-organic frameworks (MOFs) are a class of materials composed of metal centers linked by organic ligands. Most MOFs have porous channels, in this case, they can be widely used in gas capture and storage, gas separation, batteries, catalysis, ion exchange and drug delivery. MOFs based on s-block metals are important due to their many practical applications. These MOFs are also very interesting because the s-block MOFs often exhibit unpredictable geometry around the metal centers. In this thesis, the structures of six s-block metal (Li, Na, Cs, Mg, Ca, Sr) based MOFs involving V-shaped link, 4, 4′- sulfonyldibenzoate (SDB) are characterized by various techniques to confirm the structure of the sample obtained is consistent with the one discussed in literature. For four selected MOFs with porous channels, the behaviors of 13CO2 within frameworks are revealed by variable temperature (VT) 13C SSNMR spectroscopy. The results show the CO2 molecules are jumping between two sites in channels while rotating itself at the same time. The MOFs based on another ligand, C4O4, are also studied. Especially, USTA-280, which is a Ca based MOF, shows a high separation performance of CO2 from CH4 and C2H4 from C2H6 under ambient condition, due to rigid porous channels size. In this thesis, the behaviors of 13CO2 within frameworks are revealed by variable temperature (VT) 13C SSNMR spectroscopy; the behaviors of C2D2 within frameworks are revealed by VT 2H SSNMR spectroscopy. The results exhibit a tight interaction between adsorbed molecules and UTSA-280 frameworks.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

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