Yes / Three highly porous Zr(IV)-based metal–organic frameworks, UBMOF-8, UBMOF-9, and UBMOF-31, were synthesized by using 2,2′-diamino-4,4′-stilbenedicarboxylic acid, 4,4′-stilbenedicarboxylic acid, and combination of both linkers, respectively. The mixed-linker UBMOF-31 showed excellent hydrogen uptake of 4.9 wt% and high selectivity for adsorption of CO2 over N2 with high thermal stability and moderate water stability with permanent porosity and surface area of 2552 m2 g−1. / University of Bath; Royal Society of Chemistry; Engineering and Physical Sciences Research Council

Yes / The synthesis of metal–organic frameworks with large three-dimensional channels that are permanently porous and chemically stable offers new opportunities in areas such as catalysis and separation. Two linkers (L1=4,4′,4′′,4′′′-([1,1′-biphenyl]-3,3′,5,5′-tetrayltetrakis(ethyne-2,1-diyl)) tetrabenzoic acid, L2=4,4′,4′′,4′′′-(pyrene-1,3,6,8-tetrayltetrakis(ethyne-2,1-diyl))tetrabenzoic acid) were used that have equivalent connectivity and dimensions but quite distinct torsional flexibility. With these, a solid solution material, [Zr6O4(OH)4(L1)2.6(L2)0.4]⋅(solvent)x, was formed that has three-dimensional crystalline permanent porosity with a surface area of over 4000 m2 g−1 that persists after immersion in water. These properties are not accessible for the isostructural phases made from the separate single linkers. / Financial support from EPSRC under EP/H000925, access to the HPC service ARCHER via EP/L000202. S.N. thanks the EU for a Marie Curie fellowship (PIEF-GA-2010-274952). C.M.-G. thanks the Spanish MINECO for a Ramón y Cajal Fellowship (RYC-2012-10894).

Yes / Pesticide contamination is a global issue, affecting nearly 44% of the global farming population, and disproportionately affecting farmers and agricultural workers in developing countries. Despite this, global pesticide usage is on the rise, with the growing demand of global food production with increasing population. Different types of porous materials, such as carbon and zeolites, have been explored for the remediation of pesticides from the environment. However, there are some limitations with these materials, especially due to lack of functional groups and relatively modest surface areas. In this regard, metal-organic frameworks (MOFs) provide us with a better alternative to conventionally used porous materials due to their versatile and highly porous structure. Recently, a number of MOFs have been studied for the extraction of pesticides from the environment as well as for targeted and controlled release of agrochemicals. Different types of pesticides and conditions have been investigated, and MOFs have proved their potential in agricultural applications. In this review, the latest studies on delivery and extraction of pesticides using MOFs are systematically reviewed, along with some recent studies on greener ways of pest control through the slow release of chemical compounds from MOF composites. Finally, we present our insights into the key issues concerning the development and translational applications of using MOFs for targeted delivery and pesticide control.

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京都大学 / 新制・課程博士 / 博士(工学) / 甲第25015号 / 工博第5192号 / 新制||工||1991(附属図書館) / 京都大学大学院工学研究科合成・生物化学専攻 / (主査)教授 古川 修平, 教授 生越 友樹, 教授 杉安 和憲 / 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) are hybrid materials and are acknowledged as an important class of functional solid-state materials with high scientific interest in academia and industry alike. Their modular nature in terms of structural and compositional diversity, tunability, high surface area, and controlled pore size renders MOFs as the ideal candidate to address various persistent challenges pertaining to gas storage/separation, catalysis, drug delivery, and smart sensing. Through the field of reticular chemistry, targeted structures can be constructed through multiple design approaches, based on preselected building blocks prior to the assembly process. This thesis illustrates the merit of the supermolecular building layer (SBL) approach for the rational construction and discovery of highly connected and porous MOFs based on rare earth cations. Specifically, the emphasis of this study is on (i) the rational design and synthesis of 3-periodic MOFs based on SBLs pillared by ditopic ligands through post-synthetic modification (PSM) and in situ reactions. (ii) The investigation of the mixed-ligand system with different lengths and geometry of ditopic ligands on the isolation of metal clusters with distinct pore sizes. (iii) Gaining an overall insight into the exploration of different synthetic pathways that control the assembly of rare earth MOFs.

The threat of chemical warfare agent (CWA) attacks has persisted into the 21st century due to the actions of terror groups and rogue states. Traditional filtration strategies for soldier protection rely on high surface area activated carbon, but these materials merely trap CWAs through weak physisorption. Metal-organic frameworks (MOFs) have emerged as promising materials to catalyze the degradation of CWAs into significantly less toxic byproducts. The precise synthetic control over the porosity, defect density, and chemical functionality of MOFs offer exciting potential of for use in CWA degradation as well as a wide variety of other applications. Developing a molecular-level understanding of gas-MOF interactions can allow for the rational design of MOFs optimized for CWA degradation. Our research investigated the fundamental interfacial interactions between CWA simulant vapors, specifically sulfur mustard (HD) simulants, and zirconium-based MOFs (Zr-MOFs). Utilizing a custom-built ultrahigh vacuum chamber with infrared spectroscopic and mass spectrometric capabilities, the adsorption mechanism, diffusion energetics, and diffusion kinetics of HD simulants were determined. For 2-chloroethyl ethyl sulfide (2-CEES), a widely used HD simulant, infrared spectroscopy revealed that adsorption within Zr-MOFs primarily proceeded through hydrogen bond formation between 2-CEES and the bridging hydroxyls on the secondary building unit of the MOFs. Through the study of 1-chloropentane and diethyl sulfide adsorption, we determined that 2-CEES forms hydrogen bonds through its chlorine atom likely due to geometric constraints within the MOF pore environment. Temperature-programmed desorption experiments aimed at determining desorption energetics reveal that 2-CEES remain adsorbed within the pores of the MOFs until high temperatures, but traditional methods of TPD analysis fail to accurately measure both the enthalpic and entropic interactions of 2-CEES desorption from a single adsorption site. Infrared spectroscopy was able to measure the diffusion of adsorbates within MOFs by tracking the rate of decrease in overall adsorbate concentrations at several temperatures. The results indicate that 2-CEES diffusion through the pores of the MOFs is a slow, activated process that is affected by the size of the pore windows and presence of hydrogen bonding sites. We speculate that diffusion is the rate limiting step in the desorption of HD simulants through Zr-MOFs at lower temperatures. Stochastic simulations were performed in an attempt to deconvolute TPD data in order to extract desorption parameters. Finally, a combination of vacuum-based and ambient-pressure spectroscopic techniques were employed to study the reaction between 2-CEES and an amine-functionalized MOF, UiO-66-NH2. Although the presence of water adsorbed within UiO 66 NH2 under ambient conditions may assist in the reactive adsorption of 2-CEES, the reaction proceeded under anhydrous conditions. / Doctor of Philosophy / Chemical warfare agents (CWAs) are some of the most toxic chemicals on the planet and their continued use by terror groups and rogue nations threaten the lives of both civilians and the warfighter. Our work was motivated by a class of high surface area, highly porous materials that have shown the ability to degrade CWAs, specifically mustard gas, into less harmful byproducts. By determining the adsorption mechanism (how and where mustard gas “sticks” to the material), diffusion rates (how quickly mustard gas can travel through the pores of to reach the binding sites), and desorption energies (how strongly mustard gas “sticks” to the binding sites), we can alter the structure of these materials and to efficiently trap mustard gas and render it harmless. In the research described in this dissertation, we examined these fundamental interactions for a series of molecules that mimic the structure of mustard gas. and linear alkanes within several metal-organic frameworks with varying pore size. We observed the size of the pore environment affects the orientation that a given molecule sticks to binding sites as well as how quickly these compounds diffuse through the MOF. While the majority of these studies were conducted in a low-pressure environment that eliminated the presence of gas molecules in the atmosphere, research that exposed a MOF to a mustard gas mimic in an ambient environment demonstrated that gas molecules present in the atmosphere, especially water, can greatly impact the chemical interactions between mustard gas and zirconium-based MOFs.