Molecular-level design of multifunctional polymers for gas capture, conversion, and energy storage applications가스 포집, 전환 및 에너지 저장용 다기능성 고분자의 분자-레벨 수준에서의 합성

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Carbon dioxide ($CO_2$) and methane ($CH_4$) are basic carbon based greenhouse gases (C1) with very high thermodynamic stability. $CO_2$ emissions originating from the consumption of fossil fuels became a serious environmental concern mainly due to global warming, climate change, or imbalance of eco-system. The Carbon Capture & Storage (CCS) technologies could not only reduce $CO_2$ levels in atmosphere, but may also facilitate the conversion of captured $CO_2$ into value-added products, or green fuels. The current approach for $CO_2$ capture is based on amine scrubbing fluids, however, this process requires significant amount of energy to regenerate the sorbent and also loss solvents along with corrosion present additional problems. Porous organic polymers have been studied extensively in recent years to address these problems due to their modularity, high surface areas and controllable pore structure and size. Furthermore, they also show exceptional thermal/moisture stability and physisorption properties, which renders these materials suitable for vacuum swing adsorption process (VSA). In order to optimize these microporous polymers for large-sale applications, in-depth understanding on synthesis and textural properties and the interaction of gas moelcules is required. $CH_4$, a primary component of natural gas, has emerged as an important energy source in recent years mainly due to its abundance and clean nature compared to other fossil fuels. In order to use natural gas as a fuel, however, it should be processed through a procedure called “hydrodesulfurization” or “natural gas sweetening” to reduce sulfur dioxide emissions from the combustion of fossil fuels, which leads to the involuntary production of elemental sulfur. Although sulfur is one of the world’s most versatile and common elements, it has a relatively limited number of large-scale applications including gunpowder and sulfuric acid production. Recently, lithium-sulfur batteries, polymeric material synthesized via copolymerization of sulfur, and various organic transformations have also emerged as important, high-value, yet relatively small-scale applications for elemental sulfur. In this thesis, the new concept of azo-functionalized microporous polymer through molecular level design and their gas uptake performance will be introduced. These azo-polymers showed unprecedented high $CO_2/N_2$ selectivity at high temperatures which is essential property in post-combustion $CO_2$ capture system. In Chapter 3, I will describe microporous polymer’s property difference depending on polymerization route. Until now, most of research activities only focused on the final polymer’s chemical nature without accounting for the textural properties for high $CO_2$ affinity. However, there are several reports on chemically ‘similar’ porous polymers, which show completely different gas uptake performances. To investigate the origin of this phenomenon, azo-functionalized micro-porous polymers were synthesized through four different polymerization routes, and the effect of polymerization routes to gas sorption properties are systematically investigated. In Chapter 4, the direct utilization of elemental sulfur in the synthesis of ultramicroporous benzothiazole polymers (BTAPs) is discussed. $CO_2$ in landfill/natural gas could be successfully separated by using BTAPs which were found to be highly porous and showed exceptional physiochemical stability. BTAPs are not only synthesized through solvent/catalyst free conditions which means low-cost, scalable solid-sorbents, but suggest novel usage of elemental sulfur to large-scale applications. Lastly in Chapter 5, orthogonal design strategy was introduced to achieve high-contents of sulfur embedded in a polymer composite for lithium-sulfur batteries. Traditional approaches to utilize sulfur for lithium-sulfur batteries, i.e., porous templates limit impregnated sulfur content due to their intrinsic pore volumes. In this approach, sulfur was incorporated in a monomer state, after then composite was formed through ring-opening polymerization, which not only allowed homogenous distribution of sulfur, but it also led to an exceptional electrochemical performance.
Advisors
Coskun, Aliresearcher코스쿤, 알리researcher
Description
한국과학기술원 :EEWS대학원,
Publisher
한국과학기술원
Issue Date
2017
Identifier
325007
Language
eng
Description

학위논문(박사) - 한국과학기술원 : EEWS대학원, 2017.2,[xi, 156 p. :]

Keywords

Carbon dioxide capture; Methane; Molecular-level Polymer Design and Synthesis; Elemental Sulfur; Lithium-Sulfur batteries; 이산화탄소 포집; 메탄; 분자 레벨 고분자 디자인 및 합성; 유황; 리튬-황 배터리

URI
http://hdl.handle.net/10203/241616
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=675600&flag=dissertation
Appears in Collection
EEW-Theses_Ph.D.(박사논문)
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