| 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.
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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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