Dokument: Synthesis and characterization of covalent triazine frameworks and imine-linked covalent organic frameworks and their application as porous filler materials in mixed-matrix membranes for gas separation
| Titel: | Synthesis and characterization of covalent triazine frameworks and imine-linked covalent organic frameworks and their application as porous filler materials in mixed-matrix membranes for gas separation | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=59968 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20220627-081631-3 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Bügel, Stefanie [Autor] | |||||||
| Dateien: |
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| Beitragende: | Prof. Dr. Janiak, Christoph [Gutachter] Prof. Dr. Ganter, Christian [Gutachter] | |||||||
| Stichwörter: | covalent triazine frameworks (CTFs); covalent organic frameworks (COFs); mixed-matrix membranes (MMMs); gas separation | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 540 Chemie | |||||||
| Beschreibung: | Covalent organic frameworks (COFs) and the subcategory of covalent triazine frameworks (CTFs) represent materials that can possess high thermal and chemical stability as well as permanent porosity. The combination of different building blocks, as well as the possibility of further functionalization, makes them attractive for applications such as gas storage and separation. By applying COFs/CTFs as filler materials in polymer membranes, the efficiency of continuous separation of gas mixtures can be increased by the resulting mixed-matrix membranes (MMMs) compared to the pure polymer membranes, which makes the application of MMMs interesting from both economic and environmental perspectives.
In this work, CTF-fluorene was synthesized via Friedel-Crafts alkylation and applied as a filler in the polymer matrices polysulfone (PSF) and Matrimid. The prepared MMMs showed a significant improvement in permeability when tested for separation efficiency with respect to an equimolar CO2/CH4 gas mixture. Incorporation of 24 weight percent (wt%) of the filler material CTF-fluorene into a PSF matrix increased the CO2 and CH4 permeability from 5.4 and 0.19 Barrer for the pure PSF membrane to 12.8 and 0.42 Barrer for the MMM. Embedded in a Matrimid matrix, the filler material CTF-fluorene (24 wt%) increased the CO2 and CH4 permeability from 6.8 and 0.16 Barrer for the pure Matrimid membrane to 17.8 and 0.40 Barrer for the MMM. The essential contribution of filler porosity for gas transport through the membrane was confirmed by calculations of fractional free volume (FFV). Another CTF with an even higher pore volume of 0.53 cm3/g was synthesized starting from cyanuric chloride and biphenyl. The resulting structure, CTF-biphenyl, exhibited CO2 and CH4 uptakes of 1.87 mmol/g (at 0.96 bar) and 0.55 mmol/g (at 0.97 bar) at 298 K, respectively. Calculations based on the ideal adsorbed solution theory (IAST) revealed a CO2/CH4 selectivity of 10.5 at 1 bar pressure for a 50:50 (v:v) CO2/CH4 gas mixture. Subsequent CO2/CH4 mixed gas measurements of the corresponding CTF-biphenyl/Matrimid MMMs showed an increase in CO2 permeability while maintaining selectivity. Comparison with permeability models showed that the 8 wt% MMM exhibited a higher increase in permeability than expected, accompanied by a relatively higher free volume compared to the MMMs with higher filler contents. With 16 wt% CTF biphenyl, which was the optimum filler content, CO2 permeability was increased to 15.1 Barrer. This study highlighted the beneficial contribution of porosity to membrane separation performance and showed the limitations of further performance enhancement in this membrane system. Two new COFs were obtained by a Schiff base reaction. HHU-COF-1 was synthesized by the reaction of 1,3,5-tris-(4-aminophenyl)triazine with 4,4'-biphenyldicarboxaldehyde. The fluorinated analog HHU-COF-2 was obtained by applying the linker 2,2',3,3',5,5',6,6'-octafluoro-4,4'-biphenyldicarboxaldehyde. The successful formation of both structures was confirmed by solid-state NMR, infrared spectroscopy, X-ray photoelectron spectroscopy and elemental analysis. The crystalline materials were characterized by high Brunauer-Emmet-Teller (BET) surface areas of 2352 m2/g for HHU-COF-1 and 1356 m2/g for HHU-COF-2, respectively. Furthermore, larger scale syntheses were carried out and the COFs were applied to prepare MMMs with the polymer Matrimid. The application of 24 wt% of the fluorinated COF as filler material resulted in an increase in CO2 permeability from 6.8 to 13.0 Barrer with constant selectivity. In another work, the ionothermal prepared CTF-1 served as a dispersed phase in a matrix of the polymer PSF. MMMs prepared with 8, 16, and 24 wt% of the CTF were investigated in single gas permeability and selectivity studies, and a CO2 permeability increase from 7.3 to 12.7 Barrer was achieved for the 24 wt% CTF-1/PSF MMM. Constant selectivity was observed for any MMM with respect to the gas pairs O2/N2, CO2/CH4 and CO2/N2, and subsequent comparison with theoretical permeability models indicated good compatibility of the CTF with the matrix. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Chemie | |||||||
| Dokument erstellt am: | 27.06.2022 | |||||||
| Dateien geändert am: | 27.06.2022 | |||||||
| Promotionsantrag am: | 17.05.2022 | |||||||
| Datum der Promotion: | 15.06.2022 |
