1
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Brown S, Warren MR, Kubicki DJ, Fitzpatrick A, Pike SD. Photoinitiated Single-Crystal to Single-Crystal Redox Transformations of Titanium-Oxo Clusters. J Am Chem Soc 2024; 146:17325-17333. [PMID: 38865257 PMCID: PMC11212046 DOI: 10.1021/jacs.4c04068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Revised: 05/24/2024] [Accepted: 05/28/2024] [Indexed: 06/14/2024]
Abstract
Titanium-oxo clusters can undergo photochemical reactions under UV light, resulting in the reduction of the titanium-oxo core and oxidation of surface ligands. This is an important step in photocatalytic processes in light-absorbing Ti/O-based clusters, metal-organic frameworks, and (nano)material surfaces; however, studying the direct outcome of this photochemical process is challenging due to the fragility of the immediate photoproducts. In this report, titanium-oxo clusters [TiO(OiPr)(L)]n (n = 4, L = O2PPh2, or n = 6, L = O2CCH2tBu) undergo a two-electron photoredox reaction in the single-crystal state via an irreversible single-crystal to single-crystal (SC-SC) transformation initiated by a UV laser. The process is monitored by single crystal X-ray diffraction revealing the photoreduction of the cluster with coproduction of an (oxidized) acetone ligand, which is retained in the structure as a ligand to Ti(3+). The results demonstrate that photochemistry of inorganic molecules can be studied in the single crystal phase, allowing characterization of photoproducts which are unstable in the solution phase.
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Affiliation(s)
- Stephen
E. Brown
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.
| | - Mark R. Warren
- Diamond
Light Source, Harwell Science & Innovation Campus, Didcot OX11 0DE, U.K.
| | | | - Ann Fitzpatrick
- RAL
Space, Harwell Science & Innovation Campus, Didcot OX11 0QX, U.K.
| | - Sebastian D. Pike
- Department
of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.
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2
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Lätsch L, Guda SA, Romankov V, Wartmann C, Neudörfl JM, Dreiser J, Berkessel A, Guda AA, Copéret C. Tracking Coordination Environment and Reaction Intermediates in Homogeneous and Heterogeneous Epoxidation Catalysts via Ti L 2,3-Edge Near-Edge X-ray Absorption Fine Structures. J Am Chem Soc 2024; 146:7456-7466. [PMID: 38447178 DOI: 10.1021/jacs.3c12831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2024]
Abstract
Ti-based molecules and materials are ubiquitous and play a major role in both homogeneous and heterogeneous catalytic processes. Understanding the electronic structures of their active sites (oxidation state, local symmetry, and ligand environment) is key to developing molecular-level structure-property relationships. In that context, X-ray absorption spectroscopy (XAS) offers a unique combination of elemental selectivity and sensitivity to local symmetry. Commonly, for early transition metals such as Ti, K-edge XAS is applied for in situ characterization and subsequent structural analysis with high sensitivity toward tetrahedral species. Ti L2,3-edge spectroscopy is in principle complementary and offers specific opportunities to interrogate the electronic structure of five-and six-coordinated species. It is, however, much more rarely implemented because the use of soft X-rays implies ultrahigh vacuum conditions. Furthermore, the interpretation of the data can be challenging. Here, we show how Ti L2,3-edge spectroscopy can help to obtain unique information about both homogeneous and heterogeneous epoxidation catalysts and develop a molecular-level relationship between spectroscopic signatures and electronic structures. Toward this goal, we first establish a spectral library of molecular Ti reference compounds, comprising various coordination environments with mono- and dimeric Ti species having O, N, and Cl ligands. We next implemented a computational methodology based on multiplet ligand field theory and maximally localized Wannier orbitals benchmarked on our library to understand Ti L2,3-edge spectroscopic signatures. We finally used this approach to track and predict the spectra of catalytically relevant intermediates, focusing on Ti-based olefin epoxidation catalysts.
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Affiliation(s)
- Lukas Lätsch
- Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog Weg 2, CH 8093Zurich, Switzerland
| | - Sergey A Guda
- The Smart Materials Research Institute, Southern Federal University, Sladkova 178324, 344090Rostov-on-Don, Russia
| | - Vladyslav Romankov
- Swiss Light Source, Paul Scherrer Institut, CH-5232Villigen, Switzerland
| | - Christina Wartmann
- Department of Chemistry, Organic Chemistry, University of Cologne, Greinstraße 4, 50939 Cologne, Germany
| | - Jörg-M Neudörfl
- Department of Chemistry, Organic Chemistry, University of Cologne, Greinstraße 4, 50939 Cologne, Germany
| | - Jan Dreiser
- Swiss Light Source, Paul Scherrer Institut, CH-5232Villigen, Switzerland
| | - Albrecht Berkessel
- Department of Chemistry, Organic Chemistry, University of Cologne, Greinstraße 4, 50939 Cologne, Germany
| | - Alexander A Guda
- The Smart Materials Research Institute, Southern Federal University, Sladkova 178324, 344090Rostov-on-Don, Russia
| | - Christophe Copéret
- Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog Weg 2, CH 8093Zurich, Switzerland
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3
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Guli M, Helmy ET, Schneider J, Lu G, Pan JH. Characterization Methodology and Activity Evaluation of Solar-Driven Catalysts for Environmental Remediation. Top Curr Chem (Cham) 2022; 380:39. [PMID: 35951266 DOI: 10.1007/s41061-022-00394-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 05/31/2022] [Indexed: 10/15/2022]
Abstract
Solar-driven photocatalysis mediated by semiconductors has been rapidly developed as a green and sustainable technology for environmental remediation. Continuous efforts have been devoted to novel semiconducting photocatalysts to boost the efficiency of the photocatalytic system. However, controversy has widely existed in materials characterization and photocatalytic activity evaluation. This review overviews the recent advances in characterization methodology and photocatalytic activity evaluation of solar-driven catalysts (SDCs) for environmental remediation. After a general and brief introduction of different SDCs, the compositional, structural, and optical characterizations of SDCs are summarized. Moreover, the characterization methods and challenges in the doped and coupled SDCs are discussed. Finally, the challenges in the evaluation of current evaluation methods for the photocatalytic activity of SDCs are highlighted.
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Affiliation(s)
- Mina Guli
- Beijing Key Laboratory of Novel Thin Film Solar Cells, North China Electric Power University, Beijing, 102206, China
| | - Elsayed T Helmy
- Beijing Key Laboratory of Novel Thin Film Solar Cells, North China Electric Power University, Beijing, 102206, China.,Environment Division, National Institute of Oceanography and Fisheries, KayetBey, Elanfoushy, Alexandria, Egypt
| | - Jenny Schneider
- Department of Chemistry, Ludwig-Maximilians-Universität (LMU) München, Butenandtstraße 1 11, 81377, Munich, Germany
| | - Gui Lu
- Beijing Key Laboratory of Novel Thin Film Solar Cells, North China Electric Power University, Beijing, 102206, China. .,School of Energy, Power and Mechanical Engineering, North China Electric Power University, Beijing, 102206, China.
| | - Jia Hong Pan
- Beijing Key Laboratory of Novel Thin Film Solar Cells, North China Electric Power University, Beijing, 102206, China.
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4
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Abstract
The interaction of light with semiconducting materials becomes the center of a wide range of technologies, such as photocatalysis. This technology has recently attracted increasing attention due to its prospective uses in green energy and environmental remediation. The characterization of the electronic structure of the semiconductors is essential to a deep understanding of the photocatalytic process since they influence and govern the photocatalytic activity by the formation of reactive radical species. Electron paramagnetic resonance (EPR) spectroscopy is a unique analytical tool that can be employed to monitor the photoinduced phenomena occurring in the solid and liquid phases and provides precise insights into the dynamic and reactivity of the photocatalyst under different experimental conditions. This review focus on the application of EPR in the observation of paramagnetic centers formed upon irradiation of titanium dioxide and niobium oxide photocatalysts. TiO2 and Nb2O5 are very well-known semiconductors that have been widely used for photocatalytic applications. A large number of experimental results on both materials offer a reliable platform to illustrate the contribution of the EPR studies on heterogeneous photocatalysis, particularly in monitoring the photogenerated charge carriers, trap states, and surface charge transfer steps. A detailed overview of EPR-spin trapping techniques in mechanistic studies to follow the nature of the photogenerated species in suspension during the photocatalytic process is presented. The role of the electron donors or the electron acceptors and their effect on the photocatalytic process in the solid or the liquid phase are highlighted.
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5
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In-situ and operando spectroscopies for the characterization of catalysts and of mechanisms of catalytic reactions. J Catal 2021. [DOI: 10.1016/j.jcat.2021.08.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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6
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Sanz-Marco A, Hueso JL, Sebastian V, Nielsen D, Mossin S, Holgado JP, Bueno-Alejo CJ, Balas F, Santamaria J. LED-driven controlled deposition of Ni onto TiO 2 for visible-light expanded conversion of carbon dioxide into C 1-C 2 alkanes. NANOSCALE ADVANCES 2021; 3:3788-3798. [PMID: 36133006 PMCID: PMC9417592 DOI: 10.1039/d1na00021g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 04/20/2021] [Indexed: 06/15/2023]
Abstract
Photocatalytic gas-phase hydrogenation of CO2 into alkanes was achieved over TiO2-supported Ni nanoparticles under LED irradiation at 365 nm, 460 nm and white light. The photocatalysts were prepared using photo-assisted deposition of Ni salts under LED irradiation at 365 nm onto TiO2 P25 nanoparticles in methanol as a hole scavenger. This procedure yielded 2 nm Ni particles decorating the surface of TiO2 with a nickel mass content of about 2%. Before the photocatalytic runs, Ni/TiO2 was submitted to thermal reduction at 400 °C in a 10% H2 atmosphere which induced O-defective TiO2-x substrates. The formation of oxygen vacancies, Ti3+ centers and metallic Ni sites upon photocatalytic CO2 hydrogenation was confirmed by operando EPR analysis. In situ XPS under reaction conditions suggested a strong metal-support interaction and the co-existence of zero and divalent Ni states. These photoactive species enhanced the photo-assisted reduction of CO2 below 300 °C to yield CO, CH4 and C2H6 as final products.
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Affiliation(s)
- Arturo Sanz-Marco
- Department of Chemical and Environmental Engineering, University of Zaragoza c/Mariano Esquillor, s/n; Campus Rio Ebro, Edificio I+D Zaragoza 50018 Spain
- Institute of Nanoscience and Materials of Aragon (INMA), University of Zaragoza, Consejo Superior de Investigaciones Científicas (CSIC) c/Mariano Esquillor, s/n 50018 Zaragoza Spain
| | - José L Hueso
- Department of Chemical and Environmental Engineering, University of Zaragoza c/Mariano Esquillor, s/n; Campus Rio Ebro, Edificio I+D Zaragoza 50018 Spain
- Institute of Nanoscience and Materials of Aragon (INMA), University of Zaragoza, Consejo Superior de Investigaciones Científicas (CSIC) c/Mariano Esquillor, s/n 50018 Zaragoza Spain
- Networking Research Center in Biomaterials, Bioengineering and Nanomedicine (CIBER-BBN) C/Monforte de Lemos, 3-5 28029 Madrid Spain
| | - Víctor Sebastian
- Department of Chemical and Environmental Engineering, University of Zaragoza c/Mariano Esquillor, s/n; Campus Rio Ebro, Edificio I+D Zaragoza 50018 Spain
- Institute of Nanoscience and Materials of Aragon (INMA), University of Zaragoza, Consejo Superior de Investigaciones Científicas (CSIC) c/Mariano Esquillor, s/n 50018 Zaragoza Spain
- Networking Research Center in Biomaterials, Bioengineering and Nanomedicine (CIBER-BBN) C/Monforte de Lemos, 3-5 28029 Madrid Spain
| | - David Nielsen
- Centre for Catalysis and Sustainable Chemistry, Department of Chemistry, Technical University of Denmark Kemitorvet 207 2800 Kgs. Lyngby Denmark
| | - Susanne Mossin
- Centre for Catalysis and Sustainable Chemistry, Department of Chemistry, Technical University of Denmark Kemitorvet 207 2800 Kgs. Lyngby Denmark
| | - Juan P Holgado
- Instituto de Ciencia de Materiales de Sevilla (ICMS, CSIC-University of Seville) Avda. Americo Vespucio, s/n Seville 41092 Spain
| | - Carlos J Bueno-Alejo
- Department of Chemical and Environmental Engineering, University of Zaragoza c/Mariano Esquillor, s/n; Campus Rio Ebro, Edificio I+D Zaragoza 50018 Spain
- Institute of Nanoscience and Materials of Aragon (INMA), University of Zaragoza, Consejo Superior de Investigaciones Científicas (CSIC) c/Mariano Esquillor, s/n 50018 Zaragoza Spain
| | - Francisco Balas
- Department of Chemical and Environmental Engineering, University of Zaragoza c/Mariano Esquillor, s/n; Campus Rio Ebro, Edificio I+D Zaragoza 50018 Spain
- Institute of Nanoscience and Materials of Aragon (INMA), University of Zaragoza, Consejo Superior de Investigaciones Científicas (CSIC) c/Mariano Esquillor, s/n 50018 Zaragoza Spain
- Networking Research Center in Biomaterials, Bioengineering and Nanomedicine (CIBER-BBN) C/Monforte de Lemos, 3-5 28029 Madrid Spain
| | - Jesus Santamaria
- Department of Chemical and Environmental Engineering, University of Zaragoza c/Mariano Esquillor, s/n; Campus Rio Ebro, Edificio I+D Zaragoza 50018 Spain
- Institute of Nanoscience and Materials of Aragon (INMA), University of Zaragoza, Consejo Superior de Investigaciones Científicas (CSIC) c/Mariano Esquillor, s/n 50018 Zaragoza Spain
- Networking Research Center in Biomaterials, Bioengineering and Nanomedicine (CIBER-BBN) C/Monforte de Lemos, 3-5 28029 Madrid Spain
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7
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Neige E, Diwald O. Paramagnetic electron centers in BaTiO 3 nanoparticle powders. Phys Chem Chem Phys 2021; 23:12881-12888. [PMID: 34075975 DOI: 10.1039/d1cp01128f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Knowledge about the emergence and depletion of point defects in BaTiO3 (BTO) nano-structures during materials processing is key to our understanding of their later activity as components in functional dielectric devices or as photocatalysts. In this electron paramagnetic resonance (EPR) study we investigated BaTiO3 nanoparticle powders produced by flame spray pyrolysis (FSP) with powders of TiO2 anatase nanocrystals of comparable size as reference system. Paramagnetic Ti3+ ions located at regular lattice sites and with well-defined EPR signatures were measured in vacuum annealed BaTiO3 nanoparticles, which convert upon further annealing in the temperature range between 873 K and 1173 K from monocrystalline grains with an average size of d = 12 nm, BTO (873 K), to polycrystalline particles with d = 70 nm, BTO (1173 K). Whereas the starting material hosts predominantly polaron-type Ti3+ ions being surrounded by compressed O2- ion octahedra, barium-oxygen divacancy complexes, , become susceptible to electron trapping in polycrystalline and tetragonal BTO (1173 K) particles after pre-annealing at temperatures T > 873 K. The insights obtained provide a base for the detection of local distortion effects, for the identification of charge trapping sites and for the elucidation of their impact on spontaneous polarization in BaTiO3 nanoparticles as photocatalysts or dielectric components.
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Affiliation(s)
- Ellie Neige
- Department of Chemistry and Physics of Materials, Paris Lodron Universität Salzburg, Jakob-Haringer Strasse 2a, A-5020 Salzburg, Austria.
| | - Oliver Diwald
- Department of Chemistry and Physics of Materials, Paris Lodron Universität Salzburg, Jakob-Haringer Strasse 2a, A-5020 Salzburg, Austria.
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8
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Bimová P, Barbieriková Z, Grenčíková A, Šípoš R, Škulcová AB, Krivjanská A, Mackuľak T. Environmental risk of nanomaterials and nanoparticles and EPR technique as an effective tool to study them-a review. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2021; 28:22203-22220. [PMID: 33733403 DOI: 10.1007/s11356-021-13270-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 03/01/2021] [Indexed: 06/12/2023]
Abstract
Nanotechnologies and different types of nanomaterials belong in present day to intensively studied materials due to their unique properties and diverse potential applications in, e.g., electronics, medicine, or display technologies. Together with the investigation of their desired beneficial properties, a need to investigate and evaluate their influence on the environment and possible harmful effects towards living organisms is growing. This review summarizes possible toxic effects of nanomaterials on environment and living organisms, focusing on the possible bioaccumulation in organisms, toxicity, and its mechanisms. The main goal of this review is to refer to potential environmental risks rising from the use of nanomaterials and the necessity to deal with the possible toxic effects considering the growing interest in the wide-scale utilization of these materials. Electron paramagnetic resonance spectroscopy as the only analytical technique capable of detecting radical species enables detection, quantification, and monitoring of the generation of short-lived radicals often coupled with toxic effects of nanomaterials, which makes it an important method in the process of nanotoxicity mechanism determination.
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Affiliation(s)
- Paula Bimová
- Department of Inorganic Technology, Institute of Inorganic Chemistry, Technology and Materials, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 812 37, Bratislava, Slovakia.
| | - Zuzana Barbieriková
- Department of Physical Chemistry, Institute of Physical Chemistry and Chemical Physics, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 812 37, Bratislava, Slovakia
| | - Anna Grenčíková
- Department of Environmental Engineering, Institute of Chemical and Environmental Engineering, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 812 37, Bratislava, Slovakia
| | - Rastislav Šípoš
- Department of Inorganic Chemistry, Institute of Inorganic Chemistry, Technology and Materials, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 812 37, Bratislava, Slovakia
| | - Andrea Butor Škulcová
- Department of Environmental Engineering, Institute of Chemical and Environmental Engineering, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 812 37, Bratislava, Slovakia
| | - Anna Krivjanská
- Department of Environmental Engineering, Institute of Chemical and Environmental Engineering, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 812 37, Bratislava, Slovakia
| | - Tomáš Mackuľak
- Department of Environmental Engineering, Institute of Chemical and Environmental Engineering, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 812 37, Bratislava, Slovakia
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9
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Zichittella G, Polyhach Y, Tschaggelar R, Jeschke G, Pérez‐Ramírez J. Quantification of Redox Sites during Catalytic Propane Oxychlorination by Operando EPR Spectroscopy. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202013331] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Guido Zichittella
- Institute for Chemical and Bioengineering Department of Chemistry and Applied Biosciences ETH Zurich Vladimir-Prelog-Weg 1 8093 Zurich Switzerland
| | - Yevhen Polyhach
- Laboratory of Physical Chemistry Department of Chemistry and Applied Biosciences ETH Zurich Vladimir-Prelog-Weg 2 8093 Zurich Switzerland
| | - René Tschaggelar
- Laboratory of Physical Chemistry Department of Chemistry and Applied Biosciences ETH Zurich Vladimir-Prelog-Weg 2 8093 Zurich Switzerland
| | - Gunnar Jeschke
- Laboratory of Physical Chemistry Department of Chemistry and Applied Biosciences ETH Zurich Vladimir-Prelog-Weg 2 8093 Zurich Switzerland
| | - Javier Pérez‐Ramírez
- Institute for Chemical and Bioengineering Department of Chemistry and Applied Biosciences ETH Zurich Vladimir-Prelog-Weg 1 8093 Zurich Switzerland
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10
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Zichittella G, Polyhach Y, Tschaggelar R, Jeschke G, Pérez-Ramírez J. Quantification of Redox Sites during Catalytic Propane Oxychlorination by Operando EPR Spectroscopy. Angew Chem Int Ed Engl 2021; 60:3596-3602. [PMID: 33166088 DOI: 10.1002/anie.202013331] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Indexed: 11/06/2022]
Abstract
Identification and quantification of redox-active centers at relevant conditions for catalysis is pivotal to understand reaction mechanisms and requires development of advanced operando methods. Herein, we demonstrate operando EPR spectroscopy as an important technique to quantify the oxidation state of representative CrPO4 and EuOCl catalysts during propane oxychlorination, an attractive route for propylene production. In particular, we show that the space-time-yield of C3 H6 correlates with the amount of Cr2+ and Eu2+ ions generated over the catalysts during reaction. These results provide a powerful strategy to gather quantitative understanding of selective alkane oxidation, which could potentially be extrapolated to other functionalization approaches and operating conditions.
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Affiliation(s)
- Guido Zichittella
- Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 1, 8093, Zurich, Switzerland
| | - Yevhen Polyhach
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 2, 8093, Zurich, Switzerland
| | - René Tschaggelar
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 2, 8093, Zurich, Switzerland
| | - Gunnar Jeschke
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 2, 8093, Zurich, Switzerland
| | - Javier Pérez-Ramírez
- Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 1, 8093, Zurich, Switzerland
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11
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Actis A, Salvadori E, Chiesa M. Framework coordination of single-ion Cu 2+ sites in hydrated 17O-ZSM-5 zeolite. Catal Sci Technol 2021. [DOI: 10.1039/d1cy00838b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The interfacial coordination chemistry of water solvated single Cu2+ sites in ZSM-5 is assessed through pulsed EPR spectroscopy and selective 17O isotopic labelling.
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Affiliation(s)
- Arianna Actis
- Department of Chemistry and NIS Centre
- University of Torino
- 10125 Torino
- Italy
| | - Enrico Salvadori
- Department of Chemistry and NIS Centre
- University of Torino
- 10125 Torino
- Italy
| | - Mario Chiesa
- Department of Chemistry and NIS Centre
- University of Torino
- 10125 Torino
- Italy
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12
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13
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Salvadori E, Chiesa M, Buonerba A, Grassi A. Structure and dynamics of catalytically competent but labile paramagnetic metal-hydrides: the Ti(iii)-H in homogeneous olefin polymerization. Chem Sci 2020; 11:12436-12445. [PMID: 34123229 PMCID: PMC8162776 DOI: 10.1039/d0sc04967k] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 09/24/2020] [Indexed: 11/29/2022] Open
Abstract
Metal hydride complexes find widespread application in catalysis and their properties are often understood on the basis of the available crystal structures. However, some catalytically relevant metal hydrides are only spontaneously formed in situ, cannot be isolated in large quantities or crystallised and their structure is therefore ill defined. One such example is the paramagnetic Ti(iii)-hydride involved in homogeneous Ziegler-Natta catalysis, formed upon activation of CpTi(iv)Cl3 with modified methylalumoxane (MMAO). In this contribution, through a combined use of electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR) and hyperfine sublevel correlation (HYSCORE) spectroscopies we identify the nature of the ligands, their bonding interaction and the extent of the spin distribution. From the data, an atomistic and electronic model is proposed, which supports the presence of a self-assembled ion pair between a cationic terminal Ti-hydride and an aluminate anion, with a hydrodynamic radius of ca. 16 Å.
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Affiliation(s)
- Enrico Salvadori
- Department of Chemistry, University of Turin Via Pietro Giuria 7 Torino 10125 Italy
| | - Mario Chiesa
- Department of Chemistry, University of Turin Via Pietro Giuria 7 Torino 10125 Italy
| | - Antonio Buonerba
- Dipartimento di Chimica e Biologia, Università degli Studi di Salerno Via Giovanni Paolo II, 132 I-84084 Fisciano SA Italy
| | - Alfonso Grassi
- Dipartimento di Chimica e Biologia, Università degli Studi di Salerno Via Giovanni Paolo II, 132 I-84084 Fisciano SA Italy
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14
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Bakker MG, Fowler B, Bowman MK, Patience GS. Experimental methods in chemical engineering: Electron paramagnetic resonance spectroscopy‐EPR/ESR. CAN J CHEM ENG 2020. [DOI: 10.1002/cjce.23784] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Martin G. Bakker
- Department of Chemistry and BiochemistryThe University of Alabama Tuscaloosa Alabama USA
| | - Benjamin Fowler
- Department of Chemistry and BiochemistryThe University of Alabama Tuscaloosa Alabama USA
| | - Michael K. Bowman
- Department of Chemistry and BiochemistryThe University of Alabama Tuscaloosa Alabama USA
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15
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16
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Morra E, Signorile M, Salvadori E, Bordiga S, Giamello E, Chiesa M. Nature and Topology of Metal-Oxygen Binding Sites in Zeolite Materials: 17 O High-Resolution EPR Spectroscopy of Metal-Loaded ZSM-5. Angew Chem Int Ed Engl 2019; 58:12398-12403. [PMID: 31294524 DOI: 10.1002/anie.201906488] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 07/02/2019] [Indexed: 11/05/2022]
Abstract
Determining structural models is pivotal to the rational understanding and development of heterogeneous catalytic systems. A paradigmatic case is represented by open-shell metals supported on oxides, where the catalytic properties crucially depend on the nature of the metal-oxygen bonds and the extent of charge and spin transfer. Through a combination of selective 17 O isotopic enrichment and the unique properties of open-shell s-state monovalent Group 12 cations, we derive a site-specific topological description of active sites in an MFI zeolite. We show that just a few selected sites out of all possible are populated and that the relative occupancies depend on the specific properties of the metal, and we provide maps of charge and spin transfer at the metal-oxygen interface. This approach is not restricted to zeotype materials, rather it is applicable to any catalysts supported on oxygen-containing materials.
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Affiliation(s)
- Elena Morra
- Department of Chemistry, University of Torino, Via Giuria, 7, 10125, Torino, Italy
| | - Matteo Signorile
- Department of Chemistry, University of Torino, Via Giuria, 7, 10125, Torino, Italy
| | - Enrico Salvadori
- Department of Chemistry, University of Torino, Via Giuria, 7, 10125, Torino, Italy
| | - Silvia Bordiga
- Department of Chemistry, University of Torino, Via Giuria, 7, 10125, Torino, Italy
| | - Elio Giamello
- Department of Chemistry, University of Torino, Via Giuria, 7, 10125, Torino, Italy
| | - Mario Chiesa
- Department of Chemistry, University of Torino, Via Giuria, 7, 10125, Torino, Italy
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17
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Morra E, Signorile M, Salvadori E, Bordiga S, Giamello E, Chiesa M. Nature and Topology of Metal–Oxygen Binding Sites in Zeolite Materials:
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O High‐Resolution EPR Spectroscopy of Metal‐Loaded ZSM‐5. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201906488] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Elena Morra
- Department of ChemistryUniversity of Torino Via Giuria, 7 10125 Torino Italy
| | - Matteo Signorile
- Department of ChemistryUniversity of Torino Via Giuria, 7 10125 Torino Italy
| | - Enrico Salvadori
- Department of ChemistryUniversity of Torino Via Giuria, 7 10125 Torino Italy
| | - Silvia Bordiga
- Department of ChemistryUniversity of Torino Via Giuria, 7 10125 Torino Italy
| | - Elio Giamello
- Department of ChemistryUniversity of Torino Via Giuria, 7 10125 Torino Italy
| | - Mario Chiesa
- Department of ChemistryUniversity of Torino Via Giuria, 7 10125 Torino Italy
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Krämer T, Tuna F, Pike SD. Photo-redox reactivity of titanium-oxo clusters: mechanistic insight into a two-electron intramolecular process, and structural characterisation of mixed-valent Ti(iii)/Ti(iv) products. Chem Sci 2019; 10:6886-6898. [PMID: 31391912 PMCID: PMC6640198 DOI: 10.1039/c9sc01241a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 06/05/2019] [Indexed: 11/21/2022] Open
Abstract
The photo-reactivity of titanium-oxo clusters is investigated, revealing an intramolecular, solvent assisted, two-electron redox process that generates blue-coloured Ti(iii)/Ti(iv) clusters.
Small titanium-oxo-alkoxide clusters, [TiO(OR)(O2PR′2)]4, synthesised by the stoichiometric reaction of Ti(OiPr)4, phosphinic acid and water, undergo a photo-redox transformation under long-wave UV light. The photo-reaction generates blue coloured, mixed-valence Ti(iii)/Ti(iv)-oxo clusters alongside acetone and isopropanol by-products. This reactivity indicates the ability for photoactivated charge separation to occur in even the smallest of Ti-oxo clusters. EPR and NMR spectroscopic studies support a photo-redox mechanism that occurs via an intramolecular, two-electron pathway, directly relating to current doubling effects observed at TiO2 photoanodes in the presence of alcohols. The rate of photo-reaction is solvent dependent, with donor solvents supporting the formation of low coordinate Ti(iii) sites. The nature of the electronic transition is identified by DFT and TDDFT calculations as an oxygen to titanium charge transfer and it is possible to finetune the UV absorption onset observed by changing the phosphinate ligand. A two-electron photo-reduced cluster, [Ti4O4(O2PPh2)6], forms spontaneously from the photo-reaction and its structure is identified by X-ray crystallography with supporting DFT calculations. These indicate that [Ti4O4(O2PPh2)6] is high-spin and contains two ferromagnetically coupled electrons delocalised over the Ti4 core. [Ti4O4(O2PPh2)6] undergoes rapid oxidation in air in the solid-state and performs a remarkable single-crystal to single-crystal transformation, to form a stable cluster-superoxide salt.
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Affiliation(s)
- Tobias Krämer
- Department of Chemistry , Maynooth University , Maynooth , Co. Kildare , Ireland
| | - Floriana Tuna
- School of Chemistry and Photon Science Institute , University of Manchester , Oxford Road , Manchester , M13 9PL , UK
| | - Sebastian D Pike
- Department of Chemistry , University of Cambridge , Lensfield Road , CB2 1EW , UK .
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Photoelectrochemical and EPR features of polymeric C3N4 and O-modified C3N4 employed for selective photocatalytic oxidation of alcohols to aldehydes. Catal Today 2019. [DOI: 10.1016/j.cattod.2019.01.075] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Continuous Wave and Pulse EPR Characterization of Open-Shell Ti3+ Ions Generated in Hybrid SiO2–TiO2 Monoliths. Top Catal 2018. [DOI: 10.1007/s11244-018-1037-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Piovano A, Morra E, Chiesa M, Groppo E. Tuning the Ti3+ and Al3+ Synergy in an Al2O3/TiClx Catalyst To Modulate the Grade of the Produced Polyethylene. ACS Catal 2017. [DOI: 10.1021/acscatal.7b01284] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Alessandro Piovano
- Department of Chemistry,
INSTM and NIS Centre, University of Torino, via Giuria 7, 10125 Torino, Italy
| | - Elena Morra
- Department of Chemistry,
INSTM and NIS Centre, University of Torino, via Giuria 7, 10125 Torino, Italy
| | - Mario Chiesa
- Department of Chemistry,
INSTM and NIS Centre, University of Torino, via Giuria 7, 10125 Torino, Italy
| | - Elena Groppo
- Department of Chemistry,
INSTM and NIS Centre, University of Torino, via Giuria 7, 10125 Torino, Italy
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