| 1. |
- Bello-Jurado, Estefanía, et al.
(författare)
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Tunable CHA/AEI Zeolite Intergrowths with A Priori Biselective Organic Structure-Directing Agents : Controlling Enrichment and Implications for Selective Catalytic Reduction of NOx
- 2022
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 61:28
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Tidskriftsartikel (refereegranskat)abstract
- A novel ab initio methodology based on high-throughput simulations has permitted designing unique biselective organic structure-directing agents (OSDAs) that allow the efficient synthesis of CHA/AEI zeolite intergrowth materials with controlled phase compositions. Distinctive local crystallographic ordering of the CHA/AEI intergrowths was revealed at the nanoscale level using integrated differential phase contrast scanning transmission electron microscopy (iDPC STEM). These novel CHA/AEI materials have been tested for the selective catalytic reduction (SCR) of NOx, presenting an outstanding catalytic performance and hydrothermal stability, even surpassing the performance of the well-established commercial CHA-type catalyst. This methodology opens the possibility for synthetizing new zeolite intergrowths with more complex structures and unique catalytic properties.
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| 2. |
- Cho, Jungyoun, 1991-
(författare)
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Detailed structure features from 3D electron diffraction : Heteroatoms, framework disorders, and guest species in zeolites
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 3D electron diffraction (3D ED) has evolved as a powerful method for ab initio structure determination from sub micrometer-sized crystals. It can be used to elucidate the arrangement of atoms in crystalline materials and to provide insights into the laws of nature that govern the properties of matter. This thesis explores the advantages, challenges, and applications of 3D ED in structure determination of zeolites. It demonstrates that 3D ED can be used to reveal not only the framework structures but also structure details, which facilitates the study of zeolite chemistry.Zeolites are porous silicate materials used in a wide range of applications as shape-selective ion-exchangers, catalysts, and adsorbents. They feature regularly arranged pores of molecular dimensions that can discriminate between molecules with sub-Ångström precision. However, zeolites often crystallize as polycrystalline powders, and their structures are complex and difficult to determine.In this thesis, eight zeolites have been investigated by 3D ED. The structures of three novel materials, PST-24, EMM-59, and EMM-25 are determined. The silicate PST-24 exhibits columnal disorder that yields varying intracrystalline channel dimensionality, which is unprecedented in zeolites. The borosilicate EMM-59 consists of intersecting 3D 12 × 10 × 10-ring channels and is one of the most complex zeolites. The boron sites in the framework can be located by both 3D ED and integrated differential phase contrast scanning transmission electron microscopy (iDPC-STEM). Structure refinement reveals structural changes upon calcination associated to the change of boron coordination. EMM-25 is also a borosilicate with 2D 11 × 10-ring channels. 3D ED reveals that the EMM-25 structure contains zigzag chains that are disordered with two configurations. Further investigations show that similar disorders also exist in other zeolites containing zigzag chains, i.e., EU-1, ITQ-27, and nonasil. We show that disordered atomic sites that are beyond the data resolution can also be identified and refined using 3D ED data.Furthermore, factors that impact the location of organic guest species in zeolites using 3D ED are investigated. Because of the disorder and flexibility of the organic species in EMM-25 and EMM-59, only their average locations can be found using 3D ED. Therefore, we selected a STW-type zeolite HPM-1 with chiral channels for further study. HPM-1 was synthesized using 2-ethyl-1,3,4-trimethylimidazolium cations, and the guest species are intact and ordered in the channels of HPM-1, as previously determined by single crystal X-ray diffraction. We demonstrate that is possible to locate guest species using continuous rotation 3D ED data. Their atomic positions are refined against 3D ED data through both kinematical and dynamical refinements. Finally, the effect of electron fluence on the location of the organic guest species in the zeolite is investigated.
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| 3. |
- Cho, Jung, 1991-, et al.
(författare)
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The synergistic development of electron crystallography and zeolite discovery
- 2023
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 358
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Tidskriftsartikel (refereegranskat)abstract
- During the past decades, the advancement of new electron crystallographic techniques has made important impacts for the discovery of novel zeolites. High-resolution transmission electron microscopy (HRTEM) imaging directly reveals detailed structural features in zeolites, which is especially useful for studying disordered materials. 3D atomic structures of new zeolites are determined by combining HRTEM images along several projections. Electron diffraction techniques have evolved from 2D zonal-axis electron diffraction to 3D electron diffraction (3D ED), which has transformed a TEM into a single nanocrystal diffractometer for structural elucidation. The development of electron crystallography parallels the discovery of novel zeolites, where Corma's research group has played the key role and contributed to at least 30 zeolite frameworks in the Database of Zeolite Structures. Herein, we present how the ITQ zeolite materials developed by Corma's group pushed the development of electron crystallographic techniques, and how the new 3D ED techniques accelerated the discovery of novel zeolites. During the past 7 years, nearly 80% of new zeolite structures have been determined by electron crystallography. Detailed atomic structural information has been revealed from nano- and micrometer-sized crystals of extra-large pore zeolites, disordered zeolites, and low-dimensional zeolites such as nanotubes and nanosheets.
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| 4. |
- Cichocka, Magdalena Ola, 1986-, et al.
(författare)
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Aluminosilicate Zeolite EMM-28 Containing Supercavities Determined by Continuous Rotation Electron Diffraction
- 2022
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 61:29, s. 11103-11109
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Tidskriftsartikel (refereegranskat)abstract
- A new aluminosilicate zeolite, denoted EMM-28, has been successfully synthesized on a large scale using 1,1-(3,3-(1,3-phenylene)bis(propane-3,1-diyl))bis(1-methylpyrrolidinium) hydroxide as an organic structure directing agent (OSDA), which was scaled up to an ∼20 g scale with a yield of 77%. It crystallizes as thin plates (40–100 nm in thickness), and the corresponding powder X-ray diffraction (PXRD) pattern shows significant peak broadening which makes it insufficient for structure determination. Continuous rotation electron diffraction (cRED) data collected from 13 crystals were successfully used to solve and refine the structure of EMM-28. This illustrates that cRED data are capable of performing structure determination despite limited PXRD data quality. EMM-28 has a unique framework structure containing supercavities, >21 Å in size, connected by one-dimensional 10-ring channels. High-resolution transmission electron microscopy (HRTEM) confirmed the structure model. The structure of EMM-28 is related to several known zeolite structures with large cavities.
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| 5. |
- Korde, Akshay, et al.
(författare)
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Single-walled zeolitic nanotubes
- 2022
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 375:6576, s. 62-66
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Tidskriftsartikel (refereegranskat)abstract
- We report the synthesis and structure of single-walled aluminosilicate nanotubes with microporous zeolitic walls. This quasi-one-dimensional zeolite is assembled by a bolaform structure-directing agent (SDA) containing a central biphenyl group connected by C10 alkyl chains to quinuclidinium end groups. High-resolution electron microscopy and diffraction, along with other supporting methods, revealed a unique wall structure that is a hybrid of characteristic building layers from two zeolite structure types, beta and MFI. This hybrid structure arises from minimization of strain energy during the formation of a curved nanotube wall. Nanotube formation involves the early appearance of a mesostructure due to self-assembly of the SDA molecules. The biphenyl core groups of the SDA molecules show evidence of π stacking, whereas the peripheral quinuclidinium groups direct the microporous wall structure.
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| 6. |
- Kwon, Soonhyoung, et al.
(författare)
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One-Pot Synthesis of CHA/ERI-Type Zeolite Intergrowth from a Single Multiselective Organic Structure-Directing Agent
- 2024
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Ingår i: ACS Applied Materials and Interfaces. - 1944-8244 .- 1944-8252. ; 16:12, s. 14661-14668
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Tidskriftsartikel (refereegranskat)abstract
- We report the one-pot synthesis of a chabazite (CHA)/erionite (ERI)-type zeolite intergrowth structure characterized by adjustable extents of intergrowth enrichment and Si/Al molar ratios. This method utilizes readily synthesizable 6-azaspiro[5.6]dodecan-6-ium as the exclusive organic structure-directing agent (OSDA) within a potassium-dominant environment. High-throughput simulations were used to accurately determine the templating energy and molecular shape, facilitating the selection of an optimally biselective OSDA from among thousands of prospective candidates. The coexistence of the crystal phases, forming a distinct structure comprising disk-like CHA regions bridged by ERI-rich pillars, was corroborated via rigorous powder X-ray diffraction and integrated differential-phase contrast scanning transmission electron microscopy (iDPC S/TEM) analyses. iDPC S/TEM imaging further revealed the presence of single offretite layers dispersed within the ERI phase. The ratio of crystal phases between CHA and ERI in this type of intergrowth could be varied systematically by changing both the OSDA/Si and K/Si ratios. Two intergrown zeolite samples with different Si/Al molar ratios were tested for the selective catalytic reduction (SCR) of NOx with NH3, showing competitive catalytic performance and hydrothermal stability compared to that of the industry-standard commercial NH3-SCR catalyst, Cu-SSZ-13, prevalent in automotive applications. Collectively, this work underscores the potential of our approach for the synthesis and optimization of adjustable intergrown zeolite structures, offering competitive alternatives for key industrial processes.
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| 7. |
- Liu, Jinrong, 1995-, et al.
(författare)
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Photonic crystals with rainbow colors by centrifugation-assisted assembly of colloidal lignin nanoparticles
- 2023
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Ingår i: Nature Communications. - 2041-1723. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- Photonic crystals are optical materials that are often fabricated by assembly of particles into periodically arranged structures. However, assembly of lignin nanoparticles has been limited due to lacking methods and incomplete understanding of the interparticle forces and packing mechanisms. Here we show a centrifugation-assisted fabrication of photonic crystals with rainbow structural colors emitted from the structure covering the entire visible spectrum. Our results show that centrifugation is crucial for the formation of lignin photonic crystals, because assembly of lignin nanoparticles without centrifugation assistance leads to the formation of stripe patterns rather than photonic crystals. We further prove that the functions of centrifugation are to classify lignin nanoparticles according to their particle size and produce monodispersed particle layers that display gradient colors from red to violet. The different layers of lignin nanoparticles were assembled in a way that created semi-closed packing structures, which gave rise to coherent scattering. The diameter of the lignin nanoparticles in each color layer is smaller than that predicted by a modified Bragg’s equation. In situ optical microscope images provided additional evidence on the importance of dynamic rearrangement of lignin nanoparticles during their assembly into semi-closed packing structures. The preparation of lignin nanoparticles combined with the methodology for their classification and assembly pave the way for sustainable photonic crystals.
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| 8. |
- Nero, Mathias, 1970-, et al.
(författare)
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The Nanoscale Ordering of Cellulose in a Hierarchically Structured Hybrid Material Revealed Using Scanning Electron Diffraction
- 2023
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Ingår i: Small Methods. - 2366-9608.
-
Tidskriftsartikel (refereegranskat)abstract
- Cellulose, being a renewable and abundant biopolymer, has garnered significant attention for its unique properties and potential applications in hybrid materials. Understanding the hierarchical arrangement of cellulose nanofibers is crucial for developing cellulose-based materials with enhanced mechanical properties. In this study, the use of Scanning Electron Diffraction (SED) is presented to map the nanoscale orientation of cellulose fibers in a bio-composite material with a preserved wood cell structure. The SED data provides detailed insights into the ordering of cellulose with an extraordinary resolution of approximate to 15 nm. It enables a quantitative analysis of the fiber orientation over regions as large as entire cells. A highly organized arrangement of cellulose fibers within the secondary cell wall is observed, with a gradient of orientations toward the outer part of the wall. The in-plane fiber rotation is quantified, revealing a uniform orientation close to the middle lamella. Transversely sectioned material exhibits similar trends, suggesting a layered cell wall structure. Based on the SED data, a 3D model depicting the complex helical alignment of fibers throughout the cell wall is constructed. This study demonstrates the unique opportunities SED provides for characterizing the nanoscale hierarchical arrangement of cellulose nanofibers, empowering further research on a range of hybrid materials. Fundamental knowledge about the hierarchical arrangement of cellulose nanofiber is of great importance in developing new cellulose-based hybrid materials. Scanning electron diffraction is employed to map the cellulose nanofiber orientations throughout a wood-derived bio-based material. SED data reveals insights into cellulose alignment and enables precise quantitative fiber orientation analysis with a nanoscale spatial resolution.image
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| 9. |
- Salcedo-Abraira, Pablo, et al.
(författare)
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High Proton Conductivity of a Bismuth Phosphonate Metal-Organic Framework with Unusual Topology
- 2023
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Ingår i: Chemistry of Materials. - 0897-4756 .- 1520-5002. ; 35:11, s. 4329-4337
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Tidskriftsartikel (refereegranskat)abstract
- Despite the interest in proton exchange membrane (PEM)technologies(fuel cells and electrolyzers) for energy applications, the low stabilityof the electrolyte materials under working conditions (i.e., humidityand temperature) is one of their major limitations. Metal-organicframeworks (MOFs) have recently emerged as promising electrolytesdue to their higher stability compared with the currently appliedorganic polymers, proton conductivity, and outstanding porosity. Here,a novel robust Bi phosphonate MOF (branded as IEF-7) was successfullysynthesized and fully characterized, exhibiting an unusual topologydue to the irregular coordination geometry of the bismuth cations.Furthermore, IEF-7 exhibited potential porosity, very high chemicaland thermal stability, and free -PO3H groups involvedin its ultrahigh proton conductivity, reaching 1.39 x 10(-2) S cm(-1) at 90 degrees C and 90% relativehumidity for, at least, 3 cycles. In order to improve the consolidationand shaping of the powder for testing its ion conductivity properties,a highly MOF-loaded composite (90 wt %) was prepared by adding a protonconductive sulfonated polysulfone binder. The proton conductivityof the resulting composite was in the same order of magnitude as thecompacted MOF powder, making this polymeric composite electrolytevery promising for PEM technologies.
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| 10. |
- Samanta, Pratick, et al.
(författare)
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Coloration and Fire Retardancy of Transparent Wood Composites by Metal Ions
- 2023
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 15:50, s. 58850-58860
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Tidskriftsartikel (refereegranskat)abstract
- Transparent wood composites (TWs) offer the possibility of unique coloration effects. A colored transparent wood composite (C-TW) with enhanced fire retardancy was impregnated by metal ion solutions, followed by methyl methacrylate (MMA) impregnation and polymerization. Bleached birch wood with a preserved hierarchical structure acted as a host for metal ions. Cobalt, nickel, copper, and iron metal salts were used. The location and distribution of metal ions in C-TW as well as the mechanical performance, optical properties, and fire retardancy were investigated. The C-TW coloration is tunable by controlling the metal ion species and concentration. The metal ions reduced heat release rates and limited the production of smoke during forced combustion tests. The potential for scaled-up production was verified by fabricating samples with a dimension of 180 x 100 x 1 (l x b x h) mm(3).
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| 11. |
- Smalley, Christopher J. H., et al.
(författare)
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A structure determination protocol based on combined analysis of 3D-ED data, powder XRD data, solid-state NMR data and DFT-D calculations reveals the structure of a new polymorph of ʟ-tyrosine
- 2022
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Ingår i: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6520 .- 2041-6539. ; 13:18, s. 5277-5288
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Tidskriftsartikel (refereegranskat)abstract
- We report the crystal structure of a new polymorph of L-tyrosine (denoted the β polymorph), prepared by crystallization from the gas phase following vacuum sublimation. Structure determination was carried out by combined analysis of three-dimensional electron diffraction (3D-ED) data and powder X-ray diffraction (XRD) data. Specifically, 3D-ED data were required for reliable unit cell determination and space group assignment, with structure solution carried out independently from both 3D-ED data and powder XRD data, using the direct-space strategy for structure solution implemented using a genetic algorithm. Structure refinement was carried out both from powder XRD data, using the Rietveld profile refinement technique, and from 3D-ED data. The final refined structure was validated both by periodic DFT-D calculations, which confirm that the structure corresponds to an energy minimum on the energy landscape, and by the fact that the values of isotropic 13C NMR chemical shifts calculated for the crystal structure using DFT-D methodology are in good agreement with the experimental high-resolution solid-state 13C NMR spectrum. Based on DFT-D calculations using the PBE0-MBD method, the β polymorph is meta-stable with respect to the previously reported crystal structure of ʟ-tyrosine (now denoted the α polymorph). Crystal structure prediction calculations using the AIRSS approach suggest that there are three other plausible crystalline polymorphs of ʟ-tyrosine, with higher energy than the α and β polymorphs.
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| 12. |
- Svensson Grape, Erik, et al.
(författare)
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Bismuth gallate coordination networks inspired by an active pharmaceutical ingredient
- 2022
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 51:37, s. 14221-14227
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Tidskriftsartikel (refereegranskat)abstract
- The effect of solvent has been investigated for the synthesis of bismuth gallate compounds, of which the water-based bismuth subgallate has been used as an active pharmaceutical ingredient (API) for over a century. Using methanol as a solvent, two new bismuth gallates were acquired: first a flexible 3-periodic metal–organic framework (MOF) forms, which transforms upon extended synthesis times into a layered 2-periodic coordination polymer of the same bismuth-to-gallate ratio. The structures were determined by three-dimensional electron diffraction. Synthesis in ethanol resulted in the formation of the MOF phase, but not the layered phase. The layered material of the methanol-based synthesis was used as a Lewis acid catalyst due to its higher stability, showing a comparatively quick and regiospecific conversion of styrene oxide to 2-methoxy-2-phenylethanol, indicating the presence of open metal sites in the material. The acquisition of bismuth gallate structures of varying periodicity highlights the prospect of acquiring novel MOFs and coordination polymers from the same components of APIs.
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| 13. |
- Svensson Grape, Erik, et al.
(författare)
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Efficient removal of aqueous pharmaceutical pollutants by a robust anionic zirconium ellagate framework
- 2024
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Emerging organic contaminants (EOCs) in water, such as pharmaceutical compounds, are of growing environmental concern and there is a need to develop new materials and technologies for their efficient removal. A highly porous and exceptionally stable anionic zirconium ellagate metal-organic framework (MOF), denoted SU-102, was developed and utilized to remove EOCs from water, including real municipal wastewater treatment plant (WWTP) effluent. SU-102 adsorbs cationic EOCs with particularly high efficiencies and of the 17 pharmaceutical EOCs detected in WWTP effluent all 9 cationic species were removed with efficiencies of at least 79.0-99.6%, emphasizing the significance of framework charge on selectivity. As a second mechanism of EOC removal, SU-102 photodegraded the antibiotic sulfamethazine under visible light. SU-102 is synthesized from ellagic acid, an edible polyphenol building unit, highlighting the possibility of creating stable high-performance multifunctional materials from sustainably sourced plant-based components.
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| 14. |
- Svensson Grape, Erik, et al.
(författare)
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Structure of the active pharmaceutical ingredient bismuth subsalicylate
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Structure determination of pharmaceutical compounds is invaluable for drug development but remains challenging for those that form as small crystals with defects. Bismuth subsalicylate, among the most commercially significant bismuth compounds, is an active ingredient in over-the-counter medications such as Pepto-Bismol, used to treat dyspepsia and H. pylori infections. Despite its century-long history, the structure of bismuth subsalicylate is still under debate. Here we show that advanced electron microscopy techniques, namely three-dimensional electron diffraction and scanning transmission electron microscopy, can give insight into the structure of active pharmaceutical ingredients that are difficult to characterize using conventional methods due to their small size or intricate structural features. Hierarchical clustering analysis of three-dimensional electron diffraction data from ordered crystals of bismuth subsalicylate revealed a layered structure. A detailed investigation using high-resolution scanning transmission electron microscopy showed variations in the stacking of layers, the presence of which has likely hindered structure solution by other means. Together, these modern electron crystallography techniques provide a toolbox for structure determination of active pharmaceutical ingredients and drug discovery, demonstrated by this study of bismuth subsalicylate. Pepto-Bismol has been used to treat gastrointestinal disorders for over a century, yet the structure of its active ingredient is still under debate. Here, the authors apply electron crystallography to unveil the structure of bismuth subsalicylate.
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| 15. |
- Svensson Grape, Erik, et al.
(författare)
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Triple helix and rod structures of the antiseptic drug bibrocathol revealed by electron crystallography
- 2022
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 58:76, s. 10695-10698
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Tidskriftsartikel (refereegranskat)abstract
- Bibrocathol is an active pharmaceutical ingredient that has been used to treat eyelid diseases for over a century, yet its structure has remained unknown. 3D electron diffraction on crystals from a commercial ointment revealed two structures. These results highlight the technique's potential in structure elucidation from microcrystalline mixtures.
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| 16. |
- Tajnšek, Tia K., et al.
(författare)
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Design and degradation of permanently porous vitamin C and zinc-based metal-organic framework
- 2022
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Ingår i: Communications Chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- Bioapplication is an emerging field of metal-organic frameworks (MOF) utilization, but biocompatible MOFs with permanent porosity are still a rarity in the field. In addition, biocompatibility of MOF constituents is often overlooked when designing bioMOF systems, intended for drug delivery. Herein, we present the a Zn(II) bioMOF based on vitamin C as an independent ligand (bioNICS-1) forming a three-dimensional chiral framework with permanent microporosity. Comprehensive study of structure stability in biorelavant media in static and dynamic conditions demonstrates relatively high structure resistivity, retaining a high degree of its parent specific surface area. Robustness of the 3D framework enables a slow degradation process, resulting in controllable release of bioactive components, as confirmed by kinetic studies. BioNICS-1 can thus be considered as a suitable candidate for the design of a small drug molecule delivery system, which was demonstrated by successful loading and release of urea—a model drug for topical application—within and from the MOF pores.
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| 17. |
- Wang, Shuang, et al.
(författare)
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Two-Dimensional Cationic Aluminoborate as a New Paradigm for Highly Selective and Efficient Cr(VI) Capture from Aqueous Solution
- 2022
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Ingår i: JACS Au. - : American Chemical Society (ACS). - 2691-3704. ; 2:7, s. 1669-1678
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Tidskriftsartikel (refereegranskat)abstract
- Water pollutants existing in their oxyanion forms have high solubility and environmental mobility. To capture these anionic pollutants, cost-effective inorganic materials with cationic frameworks and outstanding removal performance are ideal adsorbents. Herein, we report that two-dimensional (2D) cationic aluminoborate BAC(10) sets a new paradigm for highly selective and efficient capture of Cr(VI) and other oxyanions from aqueous solution. The structure of Cr(VI)-exchanged BAC(10) sample (Cr(VI)@BAC(10), H0.22·Al2BO4.3·(HCrO4)0.22·2.64H2O) has been successfully solved by continuous rotation electron diffraction. The crystallographic data show that the 2D cationic layer of BAC(10) is built by AlO6 octahedra, BO4 tetrahedra, and BO3 triangles. Partial chromate ions exchanged with Cl– ions are located within the interlayer region, which are chemically bonded to the aluminoborate layer. BAC(10) shows faster adsorption kinetics compared to the commercial anion exchange resin (AER) and layered double hydroxides (LDHs), a higher maximum adsorption capacity of 139.1 mg/g than that of AER (62.77 mg/g), LDHs (81.43 mg/g), and a vast majority of cationic MOFs, and a much broader working pH range (2–10.5) than LDHs. Moreover, BAC(10) also shows excellent Cr(VI) oxyanion removal performance for a solution with a low concentration (1–10 mg/L), and the residual concentration can be reduced to below 0.05 mg/L of the WHO drinking water criterion. These superior properties indicate that BAC(10) is a promising material for remediation of Cr(VI) and other harmful oxyanions from wastewater.
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| 18. |
- Willhammar, Tom, 1982-, et al.
(författare)
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An adsorbent with flexible nanoscopic pores
- 2022
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 376:6592, s. 457-458
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Tidskriftsartikel (refereegranskat)abstract
- Nanoporous materials have large surface areas and well-defined pores at the molecular scale, making them attractive as selective adsorbents and catalysts (1). They can act as molecular sieves and have garnered interest because of their potential use as energy-efficient adsorbents for gas separation and storage applications, such as carbon capture. The adsorption properties of some of these materials suggest that interactions between the nanoporous material and the molecules or ions it adsorbs might induce a degree of structural flexibility in the pores. On page 491 of this issue, Xiong et al. (2) describe changes in the pore geometry of the industrially important zeolite ZSM-5 during the gas adsorption-desorption process. This direct observation of structural flexibility in a nanoporous material reveals ways to manipulate the dynamic behavior and function of these materials.
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| 19. |
- Willhammar, Tom, 1982-
(författare)
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Structural study of zeolites utilizing novel electron crystallographic methods : A voyage into the world of zeolite structures
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electron crystallography has evolved as a powerful method for structural characterization of a wide range of materials. It has two significant advantages over other methods for structure determination, e.g. X-ray diffraction. Electrons interact much more strongly with matter compared to X-rays and they can be focused by electromagnetic lenses to form images with atomic resolution. These advantages make electron crystallography a unique tool for characterization of crystalline materials suffering from small crystal size and complex or disordered structures. Zeolites are a class of microporous materials with significance in several applications. They often possess complex and disordered structures, which demand large efforts in the structure determination. Over the last years, two new electron crystallographic methods have been developed; the rotation electron diffraction (RED) and the structure projection reconstruction from a through-focus series of high resolution transmission electron microscopy (HRTEM) images. In this thesis, they will be applied for structure determination of four new zeolite structures, including EMM-25 and EMM-23 with two ordered structures, and ITQ-39 and ITQ-38 with disordered structures. Each of the structure solutions have different challenges to overcome. The high silica borosilicate EMM-25 was solved by the RED method. The aluminosilicate EMM-23 was solved by a combination of HRTEM and RED. The structure solution of two materials with disordered structures, ITQ-39 and ITQ-38, will be described. For materials containing disorders, structure projection images are of utmost importance. Furthermore, the mesoporosity inside hierarchically porous ZSM-5 crystals was studied by a combination of focused ion beam (FIB) and HRTEM imaging. The last part of this thesis explores STEM imaging for use in structure determination from 3D reconstruction.
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| 20. |
- Yang, Taimin, 1991-, et al.
(författare)
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Single-crystal structure determination of nanosized metal–organic frameworks by three-dimensional electron diffraction
- 2022
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Ingår i: Nature Protocols. - : Springer Science and Business Media LLC. - 1754-2189 .- 1750-2799. ; 17:10, s. 2389-2413
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Tidskriftsartikel (refereegranskat)abstract
- Metal–organic frameworks (MOFs) have attracted considerable interest due to their well-defined pore architecture and structural tunability on molecular dimensions. While single-crystal X-ray diffraction (SCXRD) has been widely used to elucidate the structures of MOFs at the atomic scale, the formation of large and well-ordered crystals is still a crucial bottleneck for structure determination. To alleviate this challenge, three-dimensional electron diffraction (3D ED) has been developed for structure determination of nano- (submicron-)sized crystals. Such 3D ED data are collected from each single crystal using transmission electron microscopy. In this protocol, we introduce the entire workflow for structural analysis of MOFs by 3D ED, from sample preparation, data acquisition and data processing to structure determination. We describe methods for crystal screening and handling of crystal agglomerates, which are crucial steps in sample preparation for single-crystal 3D ED data collection. We further present how to set up a transmission electron microscope for 3D ED data acquisition and, more importantly, offer suggestions for the optimization of data acquisition conditions. For data processing, including unit cell and space group determination, and intensity integration, we provide guidelines on how to use electron and X-ray crystallography software to process 3D ED data. Finally, we present structure determination from 3D ED data and discuss the important features associated with 3D ED data that need to be considered. We believe that this protocol provides critical details for implementing and utilizing 3D ED as a structure determination platform for nano- (submicron-)sized MOFs as well as other crystalline materials.
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