| 1. |
- Cho, Jung, et al.
(författare)
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EMM-25 : The Structure of Two-Dimensional 11 x 10 Medium-Pore Borosilicate Zeolite Unraveled Using 3D Electron Diffraction
- 2021
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 33:11, s. 4146-4153
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Tidskriftsartikel (refereegranskat)abstract
- The structure of the novel medium-pore borosilicate zeolite EMM-25 has been determined by continuous rotation electron diffraction (cRED). EMM-25 crystallizes in the space group Cmcm with unit cell parameters a = 11.055, b = 22.912, and c = 24.914 angstrom and a composition of IC4H8(C11H25N)(2)I (2)[Si112.5B3.5O232]. The EMM-25 framework possesses a two-dimensional channel system composed of 10-ring channels connected via 11-ring windows. Its channel system is analogous to that of the medium-pore zeolite NU-87 framework but with 11- rather than 12-ring windows, suggesting a different shape selectivity. EMM-25 was first obtained using 1,4-bis(N-methyl-N,N-dihexylammonium)butane as an organic structure directing agent (OSDA). Based on a molecular docking study of the OSDA within the pores of the determined framework structure, a new ammonium dication OSDA with an improved fit was devised. By using this new OSDA, the synthesis time was reduced 80%, from 52 to just 10 days. Furthermore, cRED data revealed a structural disorder of the EMM-25 framework present as swinging zigzag chains. The introduction of the disorder, which is a consequence of geometry relaxation, was crucial for an accurate structure refinement. Lastly, the cRED data from as-made EMM-25 showed residual potential consistent with the location of the OSDA position determined from the Rietveld refinement, concluding a complete refinement of the as-made structure based on the cRED data.
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| 2. |
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| 3. |
- 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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| 4. |
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| 5. |
- Guo, Peng, et al.
(författare)
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Accurate structure determination of a borosilicate zeolite EMM-26 with two-dimensional 10 x 10 ring channels using rotation electron diffraction
- 2016
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Ingår i: Inorganic Chemistry Frontiers. - : Royal Society of Chemistry (RSC). - 2052-1545 .- 2052-1553. ; 3:11, s. 1444-1448
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Tidskriftsartikel (refereegranskat)abstract
- A new borosilicate zeolite vertical bar N2H36C16 vertical bar[Si22B2O48].H2O, denoted as EMM-26, has been synthesized by employing a linear dicationic organic structure directing agent 1,6-bis(N-methylpyrrolidinium) hexane (OSDA). EMM-26 has a novel zeolite framework and contains two-dimensional (2D) intersecting 10 x 10-ring channels. Its structure was solved from sub-micrometer sized crystals using rotation electron diffraction (RED) and refined against both the RED and synchrotron powder diffraction data. We have shown for the first time that RED data alone can be used to accurately determine zeolite structures. The OSDAs can be removed from the framework generating permanent pores. EMM-26 shows good CO2 uptake and CO2/CH4 selectivity.
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| 6. |
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| 7. |
- Kapaca, Elina, et al.
(författare)
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Small Pore Aluminosilicate EMM-37 : Synthesis and Structure Determination Using Continuous Rotation Electron Diffraction
- 2019
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 58:19, s. 12854-12858
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Tidskriftsartikel (refereegranskat)abstract
- A new aluminosilicate zeolite, denoted EMM-37, with a 3D small pore channel system, has been synthesized using a diquaternary ammonium molecule as the structure directing agent (SDA) and metakaolin as the aluminum source. The structures of both as-made and calcined forms of EMM-37 were solved and refined using continuous rotation electron diffraction (cRED) data. cRED is a powerful method for the collection of 3D electron diffraction data from submicron- and nanosized crystals, which allows for successful solution and refinement of complex structures in symmetry as low as P (1) over bar.
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| 8. |
- Willhammar, Tom, et al.
(författare)
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EMM-23 : A Stable High-Silica Multidimensional Zeolite with Extra-Large Trilobe-Shaped Channels.
- 2014
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 136:39, s. 13570-3
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Tidskriftsartikel (refereegranskat)abstract
- Stable, multidimensional, and extra-large pore zeolites are desirable by industry for catalysis and separation of bulky molecules. Here we report EMM-23, the first stable, three-dimensional extra-large pore aluminosilicate zeolite. The structure of EMM-23 was determined from submicron-sized crystals by combining electron crystallography, solid-state nuclear magnetic resonance (NMR), and powder X-ray diffraction. The framework contains highly unusual trilobe-shaped pores that are bound by 21-24 tetrahedral atoms. These extra-large pores are intersected perpendicularly by a two-dimensional 10-ring channel system. Unlike most ideal zeolite frameworks that have tetrahedral sites with four next-nearest tetrahedral neighbors (Q(4) species), this unusual zeolite possesses a high density of Q(2) and Q(3) silicon species. It is the first zeolite prepared directly with Q(2) species that are intrinsic to the framework. EMM-23 is stable after calcination at 540 °C. The formation of this highly interrupted structure is facilitated by the high density of extra framework positive charge introduced by the dicationic structure directing agent.
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| 9. |
- Willhammar, Tom, et al.
(författare)
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High-Throughput Synthesis and Structure of Zeolite ZSM-43 with Two-Directional 8-Ring Channels
- 2017
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 56:15, s. 8856-8864
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Tidskriftsartikel (refereegranskat)abstract
- The aluminosilicate zeolite ZSM-43 (where ZSM = Zeolite Socony Mobil) was first synthesized more than 3 decades ago, but its chemical structure remained unsolved because of its poor crystallinity and small crystal size. Here we present optimization of the ZSM-43 synthesis using a high-throughput approach and subsequent structure determination by the combination of electron crystallographic methods and powder X-ray diffraction. The synthesis required the use of a combination of both inorganic (Cs+ and K+) and organic (choline) structure-directing agents. High-throughput synthesis enabled a screening of the synthesis conditions, which made it possible to optimize the synthesis, despite its complexity, in order to obtain a material with significantly improved crystallinity. When both rotation electron diffraction and high resolution transmission electron microscopy imaging techniques are applied, the structure of ZSM-43 could be determined. The structure of ZSM-43 is a new zeolite framework type and possesses a unique two-dimensional channel system limited by 8-ring channels ZSM-43 is stable upon calcination, and sorption measurements show that the material is suitable for adsorption of carbon dioxide as well as methane.
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