京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19235号 / 工博第4070号 / 新制||工||1628(附属図書館) / 32234 / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 田中 庸裕, 教授 佐藤 啓文, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20582号 / 工博第4362号 / 新制||工||1678(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 阿部 竜, 教授 陰山 洋, 教授 安部 武志 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21074号 / 工博第4438号 / 新制||工||1690(附属図書館) / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 田中 庸裕, 教授 梶 弘典, 教授 今堀 博 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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Metal-Organic Frameworks (MOFs), a class of porous materials realized via reticular construction of a plethora of organic linkers and metal nodes, have emerged as excellent candidates for light-harvesting compositions (LHC), photo or electrocatalysis. This is due to their ability to organize chromophores and metal nodes with desired functionalities, and remarkable porosity that allows efficient mass transfer of reactants and electrolytes. Recent studies have shown intriguing delocalized excited state of the orderly organized pigments in MOFs. Furthermore, the accessible pores/channels allow it to host complementary optical/redox active species within the frameworks by means of de novo or postsynthetic functionalization, as a manner for MOF compositions to integrate functionalities beyond photosensitizer, such as photo/electrocatalytic sites. In such multi-component assemblies, profound understanding of charge transfer and separation process is crucial to make the designed LHC efficient. Therefore, we could adopt chromophoric MOFs as a scaffold to systematically investigate photoinduced charge transfer by installing judiciously selected redox moieties into MOFs, whose unique electronic properties could define distinct electronic interplay with MOFs. From an aspect of further applications, photo-generated electrons can be utilized more efficiently by an external electric field applied on MOF films, which prolongs the charge-separation lifetime. For this purpose, sufficient electrical conductivity is necessary to allow charges delivered across the MOF film. Considering a large energy mismatch between the majority of traditional metal nodes including metal oxo clusters and carboxylic based struts, charge transport is defined by a slow hopping process, which hinders the harvesting of relatively short-lived separated charges. Hence, developing neoteric linkage chemistry is critically needed to overcome the charge-transport challenge.Keeping these points in mind, the scope of this dissertation mainly focuses on unraveling the fundamental principles of photoinduced charge transfer and separation, ground-state charge transport boosted by nontraditional coordination chemistry and incorporation of complementary redox species, and their substantial correlation with MOF-based photocatalysis, electrocatalysis and photoelectrocatalysis. The first chapter lays the foundational knowledge regarding generic properties (chemical and physical) of MOFs, and adopted typical postsynthetic functionalization method, namely, solvent-assisted ligand incorporation (SALI), and other physical processes including photoinduced charge and energy transfer among components within MOFs, and mechanism of electron transport, that has so far been understood, in MOFs driven by an external electric field and commonly used approaches to measure that. Chapter two and three reveal the rule to control photoinduced charge transfer in MOF compositions prepared by the installation of a series of zinc porphyrins possessing gradient excited-state and frontier-orbital energy that can define distinct charge-transfer driving force into the mesopore of a photosensitizing MOF, NU-1000. These compositions show potential for their utilization as artificial light-harvesting assemblies. Chapter four highlights new design for solid porous CO2 reduction catalysts realized by introducing cobalt phthalocyanine into NU-1000. Importantly, we interpreted the catalytic activity from the aspect of charge transport efficiency, by comparing with catalysts constituted by NU-1000 and different molecular catalysts. To harvest the photo-generated electrons, an external electric field can be applied on MOF films deposited on transparent electrodes under photoexcitation, for which sufficient electrical conductivity is a must. Therefore, in chapter five, a new semiconducting coordination polymer framework was developed by employing a novel carbodithioate group for the linkage with nickel(II) that extends in three dimensions, which shows enhanced, electrical conductivity (i.e. 10-6 – 10-7 S cm-1) in contrast to traditional carboxylate-based MOFs due to a more delocalized electronic feature of the carbodithioate-nickel cluster. More importantly, its unique electronic properties, especially a long-lived charge-separation state captured by transient-absorption technique, could alleviate the compromise between electrical conductivity and charge separation (resulted from bandgap) of light-harvesting material. We then extend this binding group to chromium(III), as introduced in chapter 6, leading to a paramagnetic 3D coordination polymer with metallic conductivity as opposed to its nickel counterpart.

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Research interest in Additive Manufacturing (AM) as an enabling technology for customizable parts is rapidly expanding. While much AM research focus is on high performance feedstocks and process optimization to obtain parts with improved mechanical properties, interest in the environmental applications of AM has recently increased. The lower cost and greater accessibility AM is leading to novel environmental research solutions in wastewater treatment and toxicity reduction by capitalizing on the increased affordability and accessibility of 3D printing (3DP) technologies for customizable, high surface area structures. The novelty and focus of this dissertation is exploration of Material Extrusion (MatEx) based Fused Filament Fabrication (FFF) of filled polymer composites as a disruptive technology enabler for deployable and retrievable structures in environmental media for adsorption, destruction and toxicity reduction of harmful chemicals. This dissertation addresses research questions that generally answer, "why AM for environmental applications?". The inherent layer-by-layer design provides larger surface area structures for interaction with contaminated media. Polylactic acid (PLA) was selected due to its green sources and biocompatibility relative to synthetic polymers and its wide processing window allowing shear thinning and "printability" despite the elevated viscosity and modulus of highly filled composites. The filler selected for contaminant adsorption was microporous zeolite, which has affinity for ammonia, radionuclides and Per- and Polyfluorinated Substances (PFAS). The filler selected for contaminant destruction was photocatalytic TiO2 nanoparticles which can degrade organic chemicals, harmful algal bloom toxins and PFAS. A preliminary research hurdle was overcome by demonstrating that immobilization of zeolite and TiO2 in a PLA binder matrix did not prevent adsorption or free radical release, respectively. The first major research objective involved investigation of high surface area printed PLA-zeolite geometries with different zeolite loadings and found that while ammonia was reduced, there were diminishing returns with increased loading in terms of mass standardized adsorptive performance due to insufficiently exposed zeolite. The research solution leveraged AM print process parameters to increase the macroporosity of the printed composite structure to create voids and channels allowing water infiltration and chemical adsorption to zeolite. Faster printing of larger roadways generated macrostructural voids that were maintained by extrusion at lower temperature for rapid solidification. The second research objective involved compounding different loadings and dispersion states of TiO2 in PLA to demonstrate immobilization of TiO2 closer to UV-light penetration water improves photocatalysis. Higher 32% w/w TiO2 loadings were heavily agglomerated and more difficult to print process due to high viscosity, rapid liquid-solid transition (G'>G") and particle network recovery during printer retractions, leading to nozzle clogging. Lower 20% w/w loading was more conducive to larger production printing due to lower viscosity, longer viscosity recovery times for retractions and thus generally a wider processing window. While altering twin screw processing parameters reduced TiO2 agglomerates in filaments, leading to increases in crystallinity (due to seeding effects and chain scission) and lower viscosity recovery, photocatalytic performance was not significantly improved. Evidence presented showed that larger particle agglomerates were more toward the inside of printed surfaces and thus less available to UV-light irradiation. This location of larger particles is supported by previous theoretical and empirical investigations showing larger particles migrate at a faster velocity away from the outer walls of confined extrudates within non-Newtonian flow fields due to normal forces, leaving more smaller particles toward outer surfaces. This research provided novel contributions to the environmental and AM research communities and pioneered a convergence of these fields into an interdisciplinary community of practice focused on better characterization and processing in environmental applications to improve structure-environmental property relationships. Future research should build on these findings to enhance performance through multi-functional materials that adsorb and destroy contaminants. The reactive surface area should be further increased through by high surface area designs and print parameter optimized porous structures providing a continuum of meso- to microporosity as confirmed by chemical flux and mass transfer studies for additional AM technologies (e.g., Direct Ink Write). / Doctor of Philosophy / Engineers and hobbies alike have great interest in Additive Manufacturing (AM), or 3D Printing, to customize parts and new designs. More recently, environmental scientists and engineers have turned to 3D printing to solve environmental problems due to the lower cost and user-friendliness of desktop machines. This research dissertation focuses on how 3D printing can allow for iterative improvements in customizable, high surface area structures to reduce chemical concentrations in water by either adsorbing or destroying the chemicals. Water is clearly a critical resource for ecosystems, recreation and drinking supplies as national security, human and ecosystem health are tied to clean water. This research addresses why 3D printing is interesting and effective for environmental solutions. Briefly the layer-by-layer design provides larger surface area structures for interaction with contaminated media. The common 3D printer feedstock Polylactic Acid (PLA) was selected since it is non-toxic and can be relatively easy to print even if modified by adding rigid filler particles for research. Micron-scale (zeolite) and nano-scale (Titanium Dioxide) particles were mixed with the polymer to make printable filaments to adsorb and destroy contaminants, respectively. This research demonstrated the proof-of-concept by removing ammonia, methylene blue dye and a harmful algal toxin from water. The materials produced are also applicable to both conventional organic pollutants and emerging contaminants of concern in the popular news such as Per- and Polyfluorinated Substances (PFAS), which were used as flame retardants and non-stick surfaces. This research ties the material properties of the experimental micro- and nano-composite filaments to how the materials extrude and solidify during 3D printing and how well the resulting printed structures work for reducing contaminant levels in water. Altering the parameters and conditions at which these materials are processed and 3D printed can significantly change their structure, density, porosity and distribution of particles and in turn increase effectiveness. The results provide new contributions to both the environmental and AM research communities and pioneers interdisciplinary collaborative ideas for these different subject matter experts to work together to better understand how handling and processing of these materials can improve their performance in environmental applications. New work should leverage the ideas and principles presented here to further improve performance, ease of production and scale-up of multifunctional material structures for multiple classes of chemicals that are of concern in surface and drinking water.

The present thesis is devoted to synthesis, through the environmentally friendly citrate sol-gel route, of YIn0.9O3 −ZnO near infrared reflective based pigments, having different chromophore elements (Mn, Cu, Fe), with the aim to add in binder and obtaining cool coatings. A “cool” coating for roofing consists of paint (or glaze) containing color pigments, which do not absorb the infrared portion of the solar spectrum. Cool coatings applied over buildings surface provide an effective solution for passive cooling of building indoors and influencing local outdoor microclimate, mitigating urban heat islands effect (UHIE). The primary purpose is to produce pigments according to an environmentally friendly route, using non-toxic raw materials, as well as short times and low temperatures for synthesis, and without residual waste. The resulting pigments must have high reflectance in the near-infrared so that they can be used in the field of cold paints. To realize the corresponding coatings, pigments were dispersed in two different binders (standard PMMA and industrial binder). For the most interesting pigments, in terms of NIR reflectance, other property, was decided to explore, which define these NIR reflective pigments as smart pigments for building application: the photocatalytic ability.

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No description available.