Abstract
ABSTRACT
This thesis deals with the synthesis of porous materials and their applications in gas adsorption. The thesis consists of eight chapters as follows:
The first two chapters provide a brief introduction to porous materials and gas
adsorption. Chapter 1 gives an overview of construction and characteristics of various porous materials, including activated carbons, zeolites, metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and organic porous polymers (POPs). Chapter 2 briefly introduces gas adsorption theory, such as physical and chemical adsorption, adsorption isotherms, and determination of specific surface area and pore size distribution. An overview of storage and capture of energy and greenhouse gases on porous materials is also described.
Chapters 3 and 4 describe the construction of porous carbon materials from nitrile precursors. In Chapter 3, two pure carbon materials with bimodal porosity are produced via cyclotrimerization of two aromatic tetranitriles and in situ carbonization in molten ZnCl2. The carbonization occurs by decomposition of triazine rings, which results in complete loss of nitrogen and formation of substantial mesopores. The resulting materials possess surface areas above 1200 m2 g−1 and exhibit exceptionally high H2 uptake (up to 2.34 wt% at 77 K and 1 bar) but low CO2 uptake capacity. In Chapter 4, a nitrogen-rich porous carbon is prepared via cyclotrimerization of a perfluorinated aromatic nitrile and in situ carbonization in molten ZnCl2. The carbonization occurs by means of defluorination, which leads to complete loss of fluorine and creation of additional porosity. The resulting material has a surface area of 1940 m2 g−1 and exhibits outstanding uptake capacities for CO2 (4.9 mmol g−1, 273
K and 1.0 bar), CH4 (3.9 mmol g−1, 273 K and 1.0 bar), and H2 (2.0 wt%, 77 K and 1.0 bar).
Chapters 5, 6, and 7 deal with the construction of triazatriangulenium (TATA)-based ionic porous frameworks. A variety of polycondensation reactions have been applied, but only FeCl3-promoted oxidative polymerization of thiophene-/carbazolefunctionalized TATAs generates ionic POPs (IPOPs) with considerable porosities (surface areas: 610−940 m2 g−1). Of these IPOPs, IPOP-3 exhibits the highest CO2 uptake capacity, up to 3.5 mmol g−1 at 273 K and 1.0 bar; IPOP-4 shows the strongest fluorescence and is found efficient for molecular oxygen sensing. Unexpected chlorination takes place during the oxidative polymerization, which affects not only the porosities but also photophysical properties of the resulting IPOPs. A systematic study on chlorination demonstrates that chlorination occurs on the TATA core, rather
than the peripheral pendants. The chlorination gives rise to significant red-shift of absorption/emission and reduction of fluorescence lifetime and quantum yield Transition-metal-catalyzed and organolithium-mediated reactions provide polymers with only macroporous interparticle voids and thus very low surface areas (4−51 m2 g−1). Attempts have been also made to prepare TATA-based ionic COFs (ICOFs) and ionic MOFs (IMOFs) under solvothermal conditions but so far with limited success.
Chapter 8 gives a brief summary of the thesis and tentatively points out the future directions for porous materials.
This thesis deals with the synthesis of porous materials and their applications in gas adsorption. The thesis consists of eight chapters as follows:
The first two chapters provide a brief introduction to porous materials and gas
adsorption. Chapter 1 gives an overview of construction and characteristics of various porous materials, including activated carbons, zeolites, metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and organic porous polymers (POPs). Chapter 2 briefly introduces gas adsorption theory, such as physical and chemical adsorption, adsorption isotherms, and determination of specific surface area and pore size distribution. An overview of storage and capture of energy and greenhouse gases on porous materials is also described.
Chapters 3 and 4 describe the construction of porous carbon materials from nitrile precursors. In Chapter 3, two pure carbon materials with bimodal porosity are produced via cyclotrimerization of two aromatic tetranitriles and in situ carbonization in molten ZnCl2. The carbonization occurs by decomposition of triazine rings, which results in complete loss of nitrogen and formation of substantial mesopores. The resulting materials possess surface areas above 1200 m2 g−1 and exhibit exceptionally high H2 uptake (up to 2.34 wt% at 77 K and 1 bar) but low CO2 uptake capacity. In Chapter 4, a nitrogen-rich porous carbon is prepared via cyclotrimerization of a perfluorinated aromatic nitrile and in situ carbonization in molten ZnCl2. The carbonization occurs by means of defluorination, which leads to complete loss of fluorine and creation of additional porosity. The resulting material has a surface area of 1940 m2 g−1 and exhibits outstanding uptake capacities for CO2 (4.9 mmol g−1, 273
K and 1.0 bar), CH4 (3.9 mmol g−1, 273 K and 1.0 bar), and H2 (2.0 wt%, 77 K and 1.0 bar).
Chapters 5, 6, and 7 deal with the construction of triazatriangulenium (TATA)-based ionic porous frameworks. A variety of polycondensation reactions have been applied, but only FeCl3-promoted oxidative polymerization of thiophene-/carbazolefunctionalized TATAs generates ionic POPs (IPOPs) with considerable porosities (surface areas: 610−940 m2 g−1). Of these IPOPs, IPOP-3 exhibits the highest CO2 uptake capacity, up to 3.5 mmol g−1 at 273 K and 1.0 bar; IPOP-4 shows the strongest fluorescence and is found efficient for molecular oxygen sensing. Unexpected chlorination takes place during the oxidative polymerization, which affects not only the porosities but also photophysical properties of the resulting IPOPs. A systematic study on chlorination demonstrates that chlorination occurs on the TATA core, rather
than the peripheral pendants. The chlorination gives rise to significant red-shift of absorption/emission and reduction of fluorescence lifetime and quantum yield Transition-metal-catalyzed and organolithium-mediated reactions provide polymers with only macroporous interparticle voids and thus very low surface areas (4−51 m2 g−1). Attempts have been also made to prepare TATA-based ionic COFs (ICOFs) and ionic MOFs (IMOFs) under solvothermal conditions but so far with limited success.
Chapter 8 gives a brief summary of the thesis and tentatively points out the future directions for porous materials.
| Originalsprog | Engelsk |
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| Forlag | Department of Chemistry, Faculty of Science, University of Copenhagen |
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| Antal sider | 165 |
| Status | Udgivet - 2014 |