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Núñez-Rico JL, Cabezas-Giménez J, Lillo V, Balestra SRG, Galán-Mascarós JR, Calero S, Vidal-Ferran A. TAMOF-1 as a Versatile and Predictable Chiral Stationary Phase for the Resolution of Racemic Mixtures. ACS APPLIED MATERIALS & INTERFACES 2023; 15:39594-39605. [PMID: 37579193 DOI: 10.1021/acsami.3c08843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/16/2023]
Abstract
Metal-organic frameworks (MOFs) have become promising materials for multiple applications due to their controlled dimensionality and tunable properties. The incorporation of chirality into their frameworks opens new strategies for chiral separation, a key technology in the pharmaceutical industry as each enantiomer of a racemic drug must be isolated. Here, we describe the use of a combination of computational modeling and experiments to demonstrate that high-performance liquid chromatography (HPLC) columns packed with TAMOF-1 as the chiral stationary phase are efficient, versatile, robust, and reusable with a wide array of mobile phases (polar and non-polar). As proof of concept, in this article, we report the resolution with TAMOF-1 HPLC columns of nine racemic mixtures with different molecular sizes, geometries, and functional groups. Initial in silico studies allowed us to predict plausible separations in chiral compounds from different families, including terpenes, calcium channel blockers, or P-stereogenic compounds. The experimental data confirmed the validity of the models and the robust performance of TAMOF-1 columns. The added value of in silico screening is an unprecedented achievement in chiral chromatography.
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Affiliation(s)
- José Luis Núñez-Rico
- Institute of Chemical Research of Catalonia (ICIQ-CERCA) and the Barcelona Institute of Science and Technology (BIST), Av. Països Catalans 16, 43007 Tarragona, Spain
- Department of Inorganic and Organic Chemistry and the Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona (UB), C/Martí i Franqués 1-11, 08028 Barcelona, Spain
| | - Juanjo Cabezas-Giménez
- Institute of Chemical Research of Catalonia (ICIQ-CERCA) and the Barcelona Institute of Science and Technology (BIST), Av. Països Catalans 16, 43007 Tarragona, Spain
- Department of Physical and Inorganic Chemistry, Universitat Rovira i Virgili (URV), C/Marcel lí Domingo s/n, 43007 Tarragona, Spain
| | - Vanesa Lillo
- Institute of Chemical Research of Catalonia (ICIQ-CERCA) and the Barcelona Institute of Science and Technology (BIST), Av. Països Catalans 16, 43007 Tarragona, Spain
| | - Salvador R G Balestra
- Materials Science Institute of Madrid, Spanish National Research Council (ICMM-CSIC), C/Sor Juana Inés de la Cruz, 3, 28049 Madrid, Spain
- Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, Ctra. Utrera km 1, 41013 Seville, Spain
| | - José Ramón Galán-Mascarós
- Institute of Chemical Research of Catalonia (ICIQ-CERCA) and the Barcelona Institute of Science and Technology (BIST), Av. Països Catalans 16, 43007 Tarragona, Spain
- Catalan Institution for Research and Advanced Studies (ICREA), Pg. Lluís Companys 23, 08010 Barcelona, Spain
| | - Sofía Calero
- Materials Simulation and Modelling, Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
| | - Anton Vidal-Ferran
- Department of Inorganic and Organic Chemistry and the Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona (UB), C/Martí i Franqués 1-11, 08028 Barcelona, Spain
- Catalan Institution for Research and Advanced Studies (ICREA), Pg. Lluís Companys 23, 08010 Barcelona, Spain
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2
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Jiao F, Zhang J, Cai X, Li H, Xu Y, Zhao Y, Du H. A fluoride-free siliceous STW-type zeolite synthesized using a designed organic structure-directing agent. Chem Commun (Camb) 2023; 59:1649-1652. [PMID: 36688621 DOI: 10.1039/d2cc05850b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
A pure silica STW zeolite is synthesized with no impurities under a wide range of synthesis conditions with and without fluoride by using easily available 1-methyl-1,5-diazabicyclo[4.3.0]non-5-ene (MDBN) as a template. MDBN having an appropriate size and geometry fits well in the STW cage, leading to its high specificity in structure-directing formation of zeolite STW.
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Affiliation(s)
- Feng Jiao
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China.
| | - Jun Zhang
- School of Materials and Chemical Engineering, Anhui Jianzhu University, Hefei, 230601, China
| | - Xianshu Cai
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China.
| | - Hao Li
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China.
| | - Yanan Xu
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China.
| | - Yue Zhao
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China.
| | - Hongbin Du
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China.
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3
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Li G, Yoskamtorn T, Chen W, Foo C, Zheng J, Tang C, Day S, Zheng A, Li MM, Tsang SCE. Thermal Alteration in Adsorption Sites over SAPO‐34 Zeolite. Angew Chem Int Ed Engl 2022; 61:e202204500. [PMID: 35471635 PMCID: PMC9322573 DOI: 10.1002/anie.202204500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Indexed: 11/08/2022]
Abstract
Zeolites have found tremendous applications in the chemical industry. However, the dynamic nature of their active sites under the flow of adsorbate molecules for adsorption and catalysis is unclear, especially in operando conditions, which could be different from the as‐synthesized structures. In the present study, we report a structural transformation of the adsorptive active sites in SAPO‐34 zeolite by using acetone as a probe molecule under various temperatures. The combination of solid‐state nuclear magnetic resonance, in situ variable‐temperature synchrotron X‐ray diffraction, and in situ diffuse‐reflectance infrared Fourier‐transform spectroscopy allow a clear identification and quantification that the chemisorption of acetone can convert the classical Brønsted acid site adsorption mode to an induced Frustrated Lewis Pairs adsorption mode at increasing temperatures. Such facile conversion is also supported by the calculations of ab‐initio molecular‐dynamics simulations. This work sheds new light on the importance of the dynamic structural alteration of active sites in zeolites with adsorbates at elevated temperatures.
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Affiliation(s)
- Guangchao Li
- Wolfson Catalysis Centre Department of Chemistry University of Oxford Oxford OX1 3QR UK
- Department of Applied Physics The Hong Kong Polytechnic University Hong Kong
| | | | - Wei Chen
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics National Center for Magnetic Resonance in Wuhan Wuhan Institute of Physics and Mathematics Innovation Academy for Precision Measurement Science and Technology Chinese Academy of Sciences Wuhan 430071 China
| | - Christopher Foo
- Wolfson Catalysis Centre Department of Chemistry University of Oxford Oxford OX1 3QR UK
| | - Jianwei Zheng
- Wolfson Catalysis Centre Department of Chemistry University of Oxford Oxford OX1 3QR UK
| | - Chiu Tang
- Diamond Light Source Ltd. Didcot OX11 0DE UK
| | - Sarah Day
- Diamond Light Source Ltd. Didcot OX11 0DE UK
| | - Anmin Zheng
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics National Center for Magnetic Resonance in Wuhan Wuhan Institute of Physics and Mathematics Innovation Academy for Precision Measurement Science and Technology Chinese Academy of Sciences Wuhan 430071 China
| | - Molly Meng‐Jung Li
- Department of Applied Physics The Hong Kong Polytechnic University Hong Kong
| | - Shik Chi Edman Tsang
- Wolfson Catalysis Centre Department of Chemistry University of Oxford Oxford OX1 3QR UK
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4
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Li G, Yoskamtorn T, Chen W, Foo C, Zheng J, Tang C, Day S, Zheng A, Li MM, Tsang SCE. Thermal Alteration in Adsorption Sites over SAPO‐34 Zeolite. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202204500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Guangchao Li
- Wolfson Catalysis Centre Department of Chemistry University of Oxford Oxford OX1 3QR UK
- Department of Applied Physics The Hong Kong Polytechnic University Hong Kong
| | | | - Wei Chen
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics National Center for Magnetic Resonance in Wuhan Wuhan Institute of Physics and Mathematics Innovation Academy for Precision Measurement Science and Technology Chinese Academy of Sciences Wuhan 430071 China
| | - Christopher Foo
- Wolfson Catalysis Centre Department of Chemistry University of Oxford Oxford OX1 3QR UK
| | - Jianwei Zheng
- Wolfson Catalysis Centre Department of Chemistry University of Oxford Oxford OX1 3QR UK
| | - Chiu Tang
- Diamond Light Source Ltd. Didcot OX11 0DE UK
| | - Sarah Day
- Diamond Light Source Ltd. Didcot OX11 0DE UK
| | - Anmin Zheng
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics National Center for Magnetic Resonance in Wuhan Wuhan Institute of Physics and Mathematics Innovation Academy for Precision Measurement Science and Technology Chinese Academy of Sciences Wuhan 430071 China
| | - Molly Meng‐Jung Li
- Department of Applied Physics The Hong Kong Polytechnic University Hong Kong
| | - Shik Chi Edman Tsang
- Wolfson Catalysis Centre Department of Chemistry University of Oxford Oxford OX1 3QR UK
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5
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Gao ZR, Balestra SRG, Li J, Camblor MA. Synthesis of Extra-Large Pore, Large Pore and Medium Pore Zeolites Using a Small Imidazolium Cation as the Organic Structure-Directing Agent. Chemistry 2021; 27:18109-18117. [PMID: 34730258 PMCID: PMC9299198 DOI: 10.1002/chem.202103288] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Indexed: 11/11/2022]
Abstract
One common strategy in the search for new zeolites is the use of organic structure‐directing agents (OSDA). Typically, one seeks to achieve a high specificity in the structure‐directing effect of the OSDA. This study shows, however, that an OSDA lacking strong specificity towards any particular zeolite may provide opportunities for discovery when other synthesis parameters are systematically screened. Thus, 1‐methyl‐2‐ethyl‐3‐n‐propylimidazolium has allowed to crystallize the new large/medium pore zeolite HPM‐16 as well as the recently reported extra‐large pore ‐SYT and the medium/small pore and chiral STW. The sophisticated OSDA originally affording ‐SYT and the new simple OSDA have very little in common, both in terms of size, shape and flexibility, while both may still direct the synthesis of the same zeolite. In fact, molecular simulations show that the new OSDA is located in three different positions of the ‐SYT structure, including the discrete 8MR where the original organic could not fit.
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Affiliation(s)
- Zihao Rei Gao
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas (ICMM-CSIC), c/ Sor Juana Inés de la Cruz, 3, Madrid, 28049, Spain
| | - Salvador R G Balestra
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas (ICMM-CSIC), c/ Sor Juana Inés de la Cruz, 3, Madrid, 28049, Spain
| | - Jian Li
- Berzelii Center EXSELENT on Porous Materials, Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, 10691, Sweden
| | - Miguel A Camblor
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas (ICMM-CSIC), c/ Sor Juana Inés de la Cruz, 3, Madrid, 28049, Spain
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6
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Li G, Foo C, Yi X, Chen W, Zhao P, Gao P, Yoskamtorn T, Xiao Y, Day S, Tang CC, Hou G, Zheng A, Tsang SCE. Induced Active Sites by Adsorbate in Zeotype Materials. J Am Chem Soc 2021; 143:8761-8771. [PMID: 34076425 DOI: 10.1021/jacs.1c03166] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
There has been a long debate on how and where active sites are created for molecular adsorption and catalysis in zeolites, which underpin many important industrial applications. It is well accepted that Lewis acidic sites (LASs) and basic sites (LBSs) as active sites in pristine zeolites are generally believed to be the extra-framework Al species and residue anion (OH-) species formed at fixed crystallographic positions after their synthesis. However, the dynamic interactions of adsorbates/reactants with pristine zeotype materials to "create" sites during real conditions remain largely unexplored. Herein, direct experimental observation of the establishment of induced active sites in silicoaluminophosphate (SAPO) by an adsorbate is for the first time made, which contradicts the traditional view of the fixed active sites in zeotype materials. Evidence shows that an induced frustrated Lewis pair (FLP, three-coordinated framework Al as LAS and SiO (H) as LBS) can be transiently favored for heterolytic molecular binding/reactions of competitive polar adsorbates due to their ineffective orbital overlap in the rigid framework. High-resolution magic-angle-spinning solid-state NMR, synchrotron X-ray diffraction, neutron powder diffraction, in situ diffuse reflectance infrared Fourier transform spectroscopy, and ab initio molecular dynamics demonstrate the transformation of a typical Brønsted acid site (Al(OH)Si) in SAPO zeolites to new induced FLP structure for hetereolytic binding upon adsorption of a strong polar adsorbate. Our unprecedented finding opens up a new avenue to understanding the dynamic establishment of active sites for adsorption or chemical reactions under molecular bombardment of zeolitic structures.
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Affiliation(s)
- Guangchao Li
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China.,Wolfson Catalysis Centre, Department of Chemistry, University of Oxford, Oxford OX1 3QR, U.K.,University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Christopher Foo
- Wolfson Catalysis Centre, Department of Chemistry, University of Oxford, Oxford OX1 3QR, U.K.,Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K
| | - Xianfeng Yi
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China
| | - Wei Chen
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China
| | - Pu Zhao
- Wolfson Catalysis Centre, Department of Chemistry, University of Oxford, Oxford OX1 3QR, U.K
| | - Pan Gao
- State Key Laboratory of Catalysis, National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People's Republic of China
| | - Tatchamapan Yoskamtorn
- Wolfson Catalysis Centre, Department of Chemistry, University of Oxford, Oxford OX1 3QR, U.K
| | - Yao Xiao
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China.,University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Sarah Day
- Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K
| | - Chiu C Tang
- Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K
| | - Guangjin Hou
- State Key Laboratory of Catalysis, National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People's Republic of China
| | - Anmin Zheng
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China
| | - Shik Chi Edman Tsang
- Wolfson Catalysis Centre, Department of Chemistry, University of Oxford, Oxford OX1 3QR, U.K
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Corella-Ochoa MN, Tapia JB, Rubin HN, Lillo V, González-Cobos J, Núñez-Rico JL, Balestra SR, Almora-Barrios N, Lledós M, Güell-Bara A, Cabezas-Giménez J, Escudero-Adán EC, Vidal-Ferran A, Calero S, Reynolds M, Martí-Gastaldo C, Galán-Mascarós JR. Homochiral Metal–Organic Frameworks for Enantioselective Separations in Liquid Chromatography. J Am Chem Soc 2019; 141:14306-14316. [DOI: 10.1021/jacs.9b06500] [Citation(s) in RCA: 74] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- M. Nieves Corella-Ochoa
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institut of Science and Technology (BIST), Av. Països Catalans 16, Tarragona E-43007, Spain
| | | | | | - Vanesa Lillo
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institut of Science and Technology (BIST), Av. Països Catalans 16, Tarragona E-43007, Spain
| | - Jesús González-Cobos
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institut of Science and Technology (BIST), Av. Països Catalans 16, Tarragona E-43007, Spain
| | - José Luis Núñez-Rico
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institut of Science and Technology (BIST), Av. Països Catalans 16, Tarragona E-43007, Spain
| | - Salvador R.G. Balestra
- Departament of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, Ctra. Utrera km 1, Sevilla 41013, Spain
| | - Neyvis Almora-Barrios
- Instituto de Ciencia Molecular, Universidad de Valencia, Calle Catedrático José Beltrán 2, Paterna 46980, Spain
| | - Marina Lledós
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institut of Science and Technology (BIST), Av. Països Catalans 16, Tarragona E-43007, Spain
| | - Arnau Güell-Bara
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institut of Science and Technology (BIST), Av. Països Catalans 16, Tarragona E-43007, Spain
| | - Juanjo Cabezas-Giménez
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institut of Science and Technology (BIST), Av. Països Catalans 16, Tarragona E-43007, Spain
- Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcel.lí Domingo s/n, Tarragona E-43007, Spain
| | - Eduardo C. Escudero-Adán
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institut of Science and Technology (BIST), Av. Països Catalans 16, Tarragona E-43007, Spain
| | - Anton Vidal-Ferran
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institut of Science and Technology (BIST), Av. Països Catalans 16, Tarragona E-43007, Spain
- ICREA, Passeig Lluís Companys, 23, Barcelona E-08010, Spain
| | - Sofía Calero
- Departament of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, Ctra. Utrera km 1, Sevilla 41013, Spain
- Department of Applied Physics, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands
| | | | - Carlos Martí-Gastaldo
- Instituto de Ciencia Molecular, Universidad de Valencia, Calle Catedrático José Beltrán 2, Paterna 46980, Spain
| | - José Ramón Galán-Mascarós
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institut of Science and Technology (BIST), Av. Països Catalans 16, Tarragona E-43007, Spain
- ICREA, Passeig Lluís Companys, 23, Barcelona E-08010, Spain
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8
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Davis ME. A Thirty-Year Journey to the Creation of the First Enantiomerically Enriched Molecular Sieve. ACS Catal 2018. [DOI: 10.1021/acscatal.8b03080] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mark E. Davis
- Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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9
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Introduction of Al into the HPM-1 Framework by In Situ Generated Seeds as an Alternative Methodology. APPLIED SCIENCES-BASEL 2018. [DOI: 10.3390/app8091634] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
An alternative method for the introduction of aluminum into the STW zeolitic framework is presented. HPM-1, a chiral STW zeolite with helical pores, was synthesized in the pure silica form, and an aluminum source was added by in situ generated seeds. Displacements of the peak positions in the Al samples were found in the X-ray diffractograms, indicating the possible incorporation of the heteroatom into the framework. Using an analysis of the 29Si and 27Al magic-angle spinning nuclear magnetic resonance (MAS NMR) spectra, we concluded that the aluminum was effectively introduced into the framework. The (AlTETRAHEDRAL/AlOCTAHEDRAL) ratio and its textural properties were studied to explain the catalytic ethanol conversion results at medium temperatures. The sample with the lowest Si/Al ratio showed the best results due to its higher surface area and pore volume, in comparison to those observed for the sample with the highest Si/Al ratio, and due to its higher bulk tetrahedral aluminum content, in comparison to the intermediate Si/Al ratio sample. All catalysts were selective to ethylene and diethyl ether, confirming the presence of acidic sites.
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