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- Cichocka, Magdalena Ola, et al.
(författare)
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A Porphyrinic Zirconium Metal-Organic Framework for Oxygen Reduction Reaction : Tailoring the Spacing between Active-Sites through Chain-Based Inorganic Building Units
- 2020
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 142:36, s. 15386-15395
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Tidskriftsartikel (refereegranskat)abstract
- The oxygen reduction reaction (ORR) is central in carbon-neutral energy devices. While platinum group materials have shown high activities for ORR, their practical uses are hampered by concerns over deactivation, slow kinetics, exorbitant cost, and scarce nature reserve. The low cost yet high tunability of metal-organic frameworks (MOFs) provide a unique platform for tailoring their characteristic properties as new electrocatalysts. Herein, we report a new concept of design and present stable Zr-chain-based MOFs as efficient electrocatalysts for ORR. The strategy is based on using Zr-chains to promote high chemical and redox stability and, more importantly, tailor the immobilization and packing of redox active-sites at a density that is ideal to improve the reaction kinetics. The obtained new electrocatalyst, PCN-226, thereby shows high ORR activity. We further demonstrate PCN-226 as a promising electrode material for practical applications in rechargeable Zn-air batteries, with a high peak power density of 133 mW cm(-2). Being one of the very few electrocatalytic MOFs for ORR, this work provides a new concept by designing chain-based structures to enrich the diversity of efficient electrocatalysts and MOFs.
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| 4. |
- Samperisi, Laura, 1993-, et al.
(författare)
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How to get maximum structure information from anisotropic displacement parameters obtained by three-dimensional electron diffraction : an experimental study on metal-organic frameworks
- 2022
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Ingår i: IUCrJ. - 2052-2525. ; 9, s. 480-491
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Tidskriftsartikel (refereegranskat)abstract
- Three-dimensional electron diffraction (3D ED) has been used for ab initio structure determination of various types of nanocrystals, such as metal-organic frameworks (MOFs), zeolites, metal oxides and organic crystals. These crystals are often obtained as polycrystalline powders, which are too small for singlecrystal X-ray diffraction (SCXRD). While it is now possible to obtain accurate atomic positions of nanocrystals by adopting kinematical refinement against 3D ED data, most new structures are refined with isotropic displacement parameters (U-eq), which limits the detection of possible structure disorders and atomic motions. Anisotropic displacement parameters (ADPs, U-ij) obtained by anisotropic structure refinement, on the other hand, provide information about the average displacements of atoms from their mean positions in a crystal, which can provide insights with respect to displacive disorder and flexibility. Although ADPs have been obtained from some 3D ED studies of MOFs, they are seldom mentioned or discussed in detail. We report here a detailed study and interpretation of structure models refined anisotropically against 3D ED data. Three MOF samples with different structural complexity and symmetry, namely ZIF-EC1, MIL-140C and Ga(OH)(1,4-ndc) (1,4-ndcH(2) is naphthalene-1,4-dicarboxylic acid), were chosen for the studies. We compare the ADPs refined against individual data sets and how they are affected by different data-merging strategies. Based on our results and analysis, we propose strategies for obtaining accurate structure models with interpretable ADPs based on kinematical refinement against 3D ED data. The ADPs of the obtained structure models provide clear and unambiguous information about linker motions in the MOFs.
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| 5. |
- Samperisi, Laura, et al.
(författare)
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Probing Molecular Motions in Metal-Organic Frameworks by Three-Dimensional Electron Diffraction
- 2021
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 143:43, s. 17947-17952
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Tidskriftsartikel (refereegranskat)abstract
- Flexible metal-organic frameworks (MOFs) are known for their vast functional diversities and variable pore architectures. Dynamic motions or perturbations are among the highly desired flexibilities, which are key to guest diffusion processes. Therefore, probing such motions, especially at an atomic level, is crucial for revealing the unique properties and identifying the applications of MOFs. Nuclear magnetic resonance (NMR) and single-crystal X-ray diffraction (SCXRD) are the most important techniques to characterize molecular motions but require pure samples or large single crystals (>5 x 5 x 5 mu m(3)), which are often inaccessible for MOF synthesis. Recent developments of three-dimensional electron diffraction (3D ED) have pushed the limits of single-crystal structural analysis. Accurate atomic information can be obtained by 3D ED from nanometer- and submicrometer-sized crystals and samples containing multiple phases. Here, we report the study of molecular motions by using the 3D ED method in MIL-140C and UiO-67, which are obtained as nanosized crystals coexisting in a mixture. In addition to an ab initio determination of their framework structures, we discovered that motions of the linker molecules could be revealed by observing the thermal ellipsoid models and analyzing the atomic anisotropic displacement parameters (ADPs) at room temperature (298 K) and cryogenic temperature (98 K). Interestingly, despite the same type of linker molecule occupying two symmetry-independent positions in MIL140C, we observed significantly larger motions for the isolated linkers in comparison to those reinforced by p-p stacking. With an accuracy comparable to that of SCXRD, we show for the first time that 3D ED can be a powerful tool to investigate dynamics at an atomic level, which is particularly beneficial for nanocrystalline materials and/or phase mixtures.
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| 6. |
- Samperisi, Laura, 1993-, et al.
(författare)
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Three-dimensional electron diffraction : a powerful structural characterization technique for crystal engineering
- 2022
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Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 24:15, s. 2719-2728
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Forskningsöversikt (refereegranskat)abstract
- Understanding crystal structures and behaviors is crucial for constructing and engineering crystalline materials with various properties and functions. Recent advancement in three-dimensional electron diffraction (3D ED) and its application on structural characterizations have expanded single-crystal analysis into nano-sized materials. Herein, we provide an overview on 3D ED, including its development, data collection protocols, and their applications for investigating crystal structures. We focus on metal-organic frameworks (MOFs) and small-molecule-based organic crystals, and highlight the insights provided by 3D ED such as structure-property relationships, polymorphism, hydrogen bonding, and crystal chirality, which are crucial subjects in crystal engineering. With more and more laboratories setting up 3D ED techniques, we envision that it will not only continue providing critical structural information, but also establish a wide impact on chemistry, materials science and life science.
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| 7. |
- Samperisi, Laura, 1993-
(författare)
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Three-dimensional electron diffraction for studying order, disorder and flexibility in metal-organic frameworks
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Metal-organic frameworks (MOFs) represent a class of 3D crystalline porous materials composed of organic linkers and metal nodes. Over the years, tens of thousands of MOF architectures have been developed, addressing various applications such as gas storage and separation, catalysis, chemical sensing, ion exchange and drug delivery. One of the most fascinating properties of MOFs lies in their flexible character responsible, for example, for the rotational dynamics of linkers. Three-dimensional electron diffraction (3D ED) has shown to be a powerful tool to solve the structure of nano- or submicrometer-sized crystals coexisting in mixtures, overcoming the limitations of x-ray diffraction. In this thesis the great potential of one continuous 3D ED protocol, namely continuous rotation electron diffraction (cRED), for the investigation of MOFs is described. cRED has routinely been used in the past decade for obtaining accurate atomic coordinates and perform structure determination of MOFs. In this thesis it is introduced how the limits of the classical approaches for structure determination by cRED can be tackled by individually adjusting the strategies to the requirements of the structures. Thanks to these approaches, full determination of complex structures and fine structural features previously considered impossible to retrieve by 3D ED data, can now be achieved. The complete structure determination of MOFs with highly complex structures, low crystallinity, sensitivity to electron beam and high-vacuum, displacive disorder and long-range structural dynamics is presented. Specifically, in this thesis it is shown how it was possible to achieve the ab initio full determination of MIL-100, an architecture with a unit cell of several hundred thousand cubic Ångstroms, and the discovery of a new class of materials (M-HAF-2), with a connectivity between those of MOFs and hydrogen-bonded organic frameworks. Additionally, the displacive disorder and dynamics in UiO-67 and MIL-140C were investigated showing for the first time that 3D ED can be applied for probing displacive disorder and molecular motion by analyzing the anisotropic displacement parameters. Methods to obtain maximum structure information from anisotropic atomic displacement parameters are also provided through careful investigations of the refinement of ZIF-EC1, MIL-140C and Ga(OH)(1,4-ndc).
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| 8. |
- Zhu, Jie, et al.
(författare)
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Metal-hydrogen-pi-bonded organic frameworks
- 2022
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 51:5, s. 1927-1935
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Tidskriftsartikel (refereegranskat)abstract
- We report the synthesis and characterization of a new series of permanently porous, three-dimensional metal–organic frameworks (MOFs), M-HAF-2 (M = Fe, Ga, or In), constructed from tetratopic, hydroxamate-based, chelating linkers. The structure of M-HAF-2 was determined by three-dimensional electron diffraction (3D ED), revealing a unique interpenetrated hcb-a net topology. This unusual topology is enabled by the presence of free hydroxamic acid groups, which lead to the formation of a diverse network of cooperative interactions comprising metal–hydroxamate coordination interactions at single metal nodes, staggered π–π interactions between linkers, and H-bonding interactions between metal-coordinated and free hydroxamate groups. Such extensive, multimodal interconnectivity is reminiscent of the complex, noncovalent interaction networks of proteins and endows M-HAF-2 frameworks with high thermal and chemical stability and allows them to readily undergo postsynthetic metal ion exchange (PSE) between trivalent metal ions. We demonstrate that M-HAF-2 can serve as versatile porous materials for ionic separations, aided by one-dimensional channels lined by continuously π-stacked aromatic groups and H-bonding hydroxamate functionalities. As an addition to the small group of hydroxamic acid-based MOFs, M-HAF-2 represents a structural merger between MOFs and hydrogen-bonded organic frameworks (HOFs) and illustrates the utility of non-canonical metal-coordinating functionalities in the discovery of new bonding and topological patterns in reticular materials.
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