Browsing by Subject "Metal-organic frameworks"

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Leveraging the extracellular electron transfer pathway of Shewanella oneidensis for pollutant remediation
(2021-06-29) Springthorpe, Sarah Katherine; Keitz, Benjamin K.; Humphrey, Simon M; Webb, Lauren J; Werth, Charles J
Shewanella oneidensis is an electroactive soil bacterium that has shown promise for environmental remediation of both inorganic and organic pollutants. The bacterium accomplishes this process through extracellular electron transfer (EET), which is capable of reducing both soluble and insoluble oxidized substrates. However, like many remediation platforms that rely on metabolic activity, S. oneidensis is sensitive to high concentrations of toxic pollutants and can demonstrate slow degradation kinetics. To improve the environmental remediation capacity of S. oneidensis, we used two strategies: a) activating a synergistic effect between metabolism and material effects and b) engineering of the EET pathway (MtrCAB) for increased enzymatic activity. For the first strategy, we combine the native respiration of S. oneidensis with the high adsorption capacities of metal-organic frameworks to generate a platform for the remediation of redox-active metals. In Chapter 2, we demonstrate that S. oneidensis can respire on Fe(III)-based metal-organic frameworks via the MtrCAB pathway and that, in conjunction with continued microbial respiration, these bio-functionalized materials can be leveraged for synergistic removal of Cr(VI). In Chapter 3, we extend this platform to the recovery of Au(III) using the metal-organic framework MIL-127. In Chapter 4, we demonstrate that exogenous proteins containing produced by the yeast Yarrowia lipolytica can be used to increase the Fe(III) reduction rate of S. oneidensis. The increased production of Fe(II) can be leveraged for improved bacteria-material remediation strategies. For the second strategy, we use directed evolution and rational design to increase the activity of the outer membrane cytochrome MtrC of S. oneidensis. In Chapter 5, we demonstrate that the directed evolution of S. oneidensis MtrC results in improved degradation performance of organic dyes. Together, this work demonstrates the advantage of increasing electron flux to redox-active substrates through both material effects and protein engineering. These strategies can be implemented to improve current remediation platforms that rely on adsorption or bacterial metabolism.
Novel multifunctional porous coordination polymers from pre-synthetically modified organophosphorus ligands
(2015-05) Bohnsack, Alisha Marie; Humphrey, Simon M.; Holliday, Bradley J.; Rose, Michael J.; Krische, Michael J.; Demkov, Alexander A.
Phosphine-based Porous Coordination Polymers (PCPs) have shown promising results as gas storage, gas separations, and molecular sensing materials due the versatility of the P(III)/P(V) chemistry, coupled with the inherent 3-dimensionality of the ligands. A variety of pre-synthetically modified organophosphine linkers have been reacted with alkali earth metals, early transition metals, and lanthanides to produce a series of Phosphine Coordination Materials (PCMs) with a wide array of topologies and pore functionalities. A p-carboxylated triphenylphosphine oxide linker, tctpoH₃, has been reacted with Mg(II) to form the thermally robust PCM-11, which possesses superior room-temperature CO₂ adsorption capacity at 12 bar. A new tetrahedral phosphonium salt, tctp⁺H₃, has been synthesized by the Pd(II)-catalyzed reaction of p-carboxylated triphenylphosphine with 4-iodobenzoic acid to produce a zwitterionic monophosphine precursor. Upon examination of its crystal structure, it was found that tctp⁺H₃ possesses a high degree of hydrogen-bonding between neighboring carboxylic acid groups, which causes it to polymerize into a porous, metal-free, ionically-bonded coordination polymer, iPCM-1. This phosphonium linker has been reacted with a series of Ln(III) precursors to form an isostructural set of PCMs that exhibit characteristic lanthanide luminescence properties. Several PCPs have been developed from a new bis(phosphine)MCl₂ (M = Pd, Pt) complex upon reaction with early transition metals. Zn(II)-based PCM-18 exhibits unusual and fully reversible H₂ adsorption at 150 °C, as well as post-synthetic reactivity inside the pores of the material. Co(II)-based PCM-24 also displays similar high-temperature H₂ sorption behavior, along with a reversible pink to blue color change upon activation, indicative of a symmetry transformation from O [subscript h] to T [subscript d] about the metal node.
Syntheses of calix[4]pyrrole functionalized extended molecular systems and applications for environmental concerns
(2017-09-13) Lee, Juhoon; Sessler, Jonathan L.; Anslyn, Eric V.; Liu, Hung-wen; Humphrey, Simon M.; Brodbelt, Jennifer S.
Considerable efforts have been made to develop the supramolecular systems being capable of selectively binding and recognizing specific chemical species. Within this context, particular has been put towards nuclear waste remediation, environmental chemistry, and biology. Calix[4]pyrroles are non-conjugated tetrapyrrolic macrocycles capable of binding anions and neutral substrates via concerted and directional hydrogen bonding. Moreover, functionalization of the calix[4]pyrrole meso position allows the incorporation of additional binding sites for both cations and anions. Due to the ease of preparation and functionalization, elaborated calix[4]pyrroles have been employed as various anion and ion pair receptors as well as potential extractants for species present in high-level liquid waste (HLLW) and transporters for biological important ions in connection with therapeutic aims. These studies reported herein are primarily focused on the discovery in meso-substituted calix[4]pyrrole-functionalized extended molecular systems and applications for environmental concerns. Chapter 1 provides a brief overview regarding the historical perspective and inherent properties of calix[4]pyrroles, as well as outlines recent contributions for capturing, extracting and sequestering chemical species with environmental concerns. Chapter 2 describes the extraction of the sulfate anion via bipyrrole-strapped calix[4]pyrroles. Through these studies, we have discovered such cryptand-like receptors could extract the highly hydrophilic sulfate anion into an organic solvent from aqueous solutions when A336Cl was used as a coextractant. Chapter 3 depicts a novel meso-functionalized calix[4]pyrrole-based three dimensional networked molecular cage. Interestingly, upon treatment of fluoride, the resultant framework could be disassembled, which serves to release the inner molecules. Moreover, multiple lone pairs and hydrogen bonding donors provided by the calix[4]pyrrole building units allow for a highly selective adsorption for CO2 over other gaseous guest, such as N2, O2, H2 and CH4. Chapter 4 describes two novel calix[4]pyrrole-based uranyl complex cages, cage-1 and -2. The transformation from a tripodal cage (cage-1) to a tetrapodal system (cage-2) was achieved by a sunlight induced photochemical oxidation or via simple addition of hydrogen peroxide. Chapter 5 details the synthetic procedures and characterizations of all compounds used in these studies.
The terthiophene-based imidazole derivative : electropolymerization of its new N-heterocyclic carbene (NHC) complexes and its new dual functional metal-organic framework
(2019-11-25) Wang, Weiran; Jones, Richard A., 1954-; Ekerdt, John G; Rose, Michael J; Que, Emily L
Synthesizing new thiophene-based molecules with unique electronic, photophysical and catalytic properties can lead to the discovery of new functional solid-state materials (e.g. conductive polymers and metal-organic frameworks (MOFs)). Thiophene-based conducting polymers have intrinsic electronic properties with a narrow bandgap (~2.0 eV), outstanding stabilities and structural functionalities, that can be synthesized through electrochemical oxidation onto a conductive electrode. Upon incorporation with metal complexes, thiophene-based metallopolymers can further be used as sensors, light-emitting diodes and energy generation/storage materials. Metal-organic frameworks (MOFs) are porous crystalline materials constructed from metal centers as secondary building blocks (SBUs) and organic linkers. Their permanent porous nature with large surface areas allows for the recognition of small quantities of materials and the absorption of various guest molecules, thus achieving applications such as excellent gas absorption/storage, sensing and heterogenous catalytic activity. In this work, a novel series of thiophene-based imidazole (ThIM and TThIM) and imidazolium iodide molecules (ThIMeHI and TThIMeHI) were synthesized in good yields and their photophysical properties were studied. Solid-state materials synthesized from these new emissive molecules were found to possess new properties. The imidazolium iodide derivatives, ThIMeHI and TThIMeHI, were further developed into a new series of N-heterocyclic carbene (NHC) ligands and their palladium, platinum, iridium and rhodium complexes were synthesized and characterized by single crystal X-ray diffraction studies. Their photophysical properties, different polymorphic forms and catalytic activities were then studied accordingly. These metal complexes were further electropolymerized to synthesize conductive metallopolymer thin films. UV-vis-NIR spectroelectrochemistry data of these conductive polymer thin films showed reversible color changes upon oxidation due to the generation of charge carrier species along the polythiophene backbones. TThIM can be further functionalized as the emissive dicarboxylic acid (TIBTCH₂). This new emissive organic linker was incorporated into a 3-dimensional MOF with tri-manganese SBUs. The solid-state photophysical behavior and magnetic properties of this new MOF were studied accordingly.