Generation of gold nanoclusters encapsulated in an MCM-22 zeolite for the aerobic oxidation of cyclohexane

[EN] In this work, we will report the generation of Au clusters in a purely siliceous MCM-22 zeolite. The catalytic properties of these Au clusters have been tested for the selective oxidation of cyclohexane to cyclohexanol and cyclohexanone (KA-oil). The Au clusters encapsulated in the MCM-22 zeolite are highly active and selective for the oxidation of cyclohexane to KA-oil, which is superior to Au nanoparticles on the same support. These results suggest that Au clusters are highly active for the activation of oxygen to produce radical species.This work has been supported by the European Union through the European Research Council (grant ERC-AdG-2014-671093, SynCatMatch) and the Spanish government through the "Severo Ochoa Program" (SEV-2016-0683). The authors also thank the Microscopy Service of UPV for kind help with TEM and STEM measurements. Mr J. A. Gaona is greatly acknowledged for his very helpful assistance on the catalytic studies. The XAS data were acquired at European Synchrotron Radiation Facility. The HAADF-HRSTEM studies were conducted in the Laboratorio de Microscopias Avanzadas (LMA) at the Instituto de Nanociencia de Aragon (INA)-Universidad de Zaragoza (Spain), Spanish ICTS National facility. R. A. gratefully acknowledges the support from the Spanish Ministry of Economy and Competitiveness (MINECO) through project grant MAT2016-79776-P (AEI/FEDER, UE).Liu, L.; Arenal, R.; Meira, DM.; Corma Canós, A. (2019). Generation of gold nanoclusters encapsulated in an MCM-22 zeolite for the aerobic oxidation of cyclohexane. Chemical Communications. 55(11):1607-1610. https://doi.org/10.1039/c8cc07185cS160716105511Claus, P. (2005). Heterogeneously catalysed hydrogenation using gold catalysts. Applied Catalysis A: General, 291(1-2), 222-229. doi:10.1016/j.apcata.2004.12.048Hashmi, A. S. K., & Hutchings, G. J. (2006). Gold Catalysis. 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J., Navas, J., Yacaman, M. J., … Mayoral, A. (2013). Exceptional oxidation activity with size-controlled supported gold clusters of low atomicity. Nature Chemistry, 5(9), 775-781. doi:10.1038/nchem.1721Boronat, M., Leyva-Pérez, A., & Corma, A. (2013). Theoretical and Experimental Insights into the Origin of the Catalytic Activity of Subnanometric Gold Clusters: Attempts to Predict Reactivity with Clusters and Nanoparticles of Gold. Accounts of Chemical Research, 47(3), 834-844. doi:10.1021/ar400068wYamazoe, S., Koyasu, K., & Tsukuda, T. (2013). Nonscalable Oxidation Catalysis of Gold Clusters. Accounts of Chemical Research, 47(3), 816-824. doi:10.1021/ar400209aBore, M. T., Pham, H. N., Switzer, E. E., Ward, T. L., Fukuoka, A., & Datye, A. K. (2005). The Role of Pore Size and Structure on the Thermal Stability of Gold Nanoparticles within Mesoporous Silica. The Journal of Physical Chemistry B, 109(7), 2873-2880. doi:10.1021/jp045917pOtto, T., Zones, S. I., & Iglesia, E. (2016). Challenges and strategies in the encapsulation and stabilization of monodisperse Au clusters within zeolites. Journal of Catalysis, 339, 195-208. doi:10.1016/j.jcat.2016.04.015Liu, L., Díaz, U., Arenal, R., Agostini, G., Concepción, P., & Corma, A. (2016). Generation of subnanometric platinum with high stability during transformation of a 2D zeolite into 3D. Nature Materials, 16(1), 132-138. doi:10.1038/nmat4757Liu, L., Zakharov, D. N., Arenal, R., Concepcion, P., Stach, E. A., & Corma, A. (2018). Evolution and stabilization of subnanometric metal species in confined space by in situ TEM. Nature Communications, 9(1). doi:10.1038/s41467-018-03012-6Xue, Y., Li, X., Li, H., & Zhang, W. (2014). Quantifying thiol–gold interactions towards the efficient strength control. Nature Communications, 5(1). doi:10.1038/ncomms5348Pensa, E., Cortés, E., Corthey, G., Carro, P., Vericat, C., Fonticelli, M. H., … Salvarezza, R. C. (2012). 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Nature Communications, 8(1). doi:10.1038/ncomms1488

Regioselective Generation of Single-Site Iridium Atoms and Their Evolution into Stabilized Subnanometric Iridium Clusters in MWW Zeolite

This is the peer reviewed version of the following article: L. Liu, M. Lopez-Haro, D. M. Meira, P. Concepcion, J. J. Calvino, A. Corma, Angew. Chem. Int. Ed. 2020, 59, 15695, which has been published in final form at https://doi.org/10.1002/anie.202005621. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.[EN] Preparation of supported metal catalysts with uniform particle size and coordination environment is a challenging and important topic in materials chemistry and catalysis. In this work, we report the regioselective generation of single-site Ir atoms and their evolution into stabilized subnanometric Ir clusters in MWW zeolite, which are located at the 10MR window connecting the two neighboring 12MR supercages. The size of the subnanometric Ir clusters can be controlled by the post-synthesis treatments and maintain below 1 nm even after being reduced at 650 degrees C, which cannot be readily achieved with samples prepared by conventional impregnation methods. The high structure sensitivity, size-dependence, of catalytic performance in the alkane hydrogenolysis reaction of Ir clusters in the subnanometric regime is evidenced.This work has been supported by the European Union through the European Research Council (grant ERC-AdG-2014-671093, SynCatMatch) and the Spanish government through the "Severo Ochoa Program" (SEV-2016-0683). The authors also thank Microscopy Service of UPV for the TEM and STEM measurements. High-resolution STEM measurements were performed at the DME-UCA node of the ELECMI National Singular Infrastruture, in Cadiz University, with financial support from FEDER/MINECO (MAT2017-87579-R and MAT2016-81118-P). This research used resources of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, and was supported by the U.S. DOE under Contract No.DE-AC02-06CH11357, and the Canadian Light Source and its funding partners. The financial support from ExxonMobil on this project is also greatly acknowledged.Liu, L.; Lopez-Haro, M.; Meira, DM.; Concepción Heydorn, P.; Calvino, JJ.; Corma Canós, A. (2020). Regioselective Generation of Single-Site Iridium Atoms and Their Evolution into Stabilized Subnanometric Iridium Clusters in MWW Zeolite. Angewandte Chemie International Edition. 59(36):15695-15702. https://doi.org/10.1002/anie.202005621S15695157025936Liu, L., & Corma, A. (2018). Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles. Chemical Reviews, 118(10), 4981-5079. doi:10.1021/acs.chemrev.7b00776Thomas, J. M., Raja, R., & Lewis, D. W. (2005). 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Angewandte Chemie, 131(51), 18743-18749. doi:10.1002/ange.201912367Liu, Y., Li, Z., Yu, Q., Chen, Y., Chai, Z., Zhao, G., … Li, Y. (2019). A General Strategy for Fabricating Isolated Single Metal Atomic Site Catalysts in Y Zeolite. Journal of the American Chemical Society, 141(23), 9305-9311. doi:10.1021/jacs.9b02936Wu, S., Yang, X., & Janiak, C. (2019). Confinement Effects in Zeolite‐Confined Noble Metals. Angewandte Chemie International Edition, 58(36), 12340-12354. doi:10.1002/anie.201900013Wu, S., Yang, X., & Janiak, C. (2019). Confinement Effects in Zeolite‐Confined Noble Metals. Angewandte Chemie, 131(36), 12468-12482. doi:10.1002/ange.201900013Liu, L., Lopez-Haro, M., Lopes, C. W., Li, C., Concepcion, P., Simonelli, L., … Corma, A. (2019). Regioselective generation and reactivity control of subnanometric platinum clusters in zeolites for high-temperature catalysis. Nature Materials, 18(8), 866-873. doi:10.1038/s41563-019-0412-6Camblor, M. 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E., Carr, R. T., Guzman, J., Casty, G. L., … Corma, A. (2016). Reversible Transformation of Pt Nanoparticles into Single Atoms inside High-Silica Chabazite Zeolite. Journal of the American Chemical Society, 138(48), 15743-15750. doi:10.1021/jacs.6b10169Liu, L., Zakharov, D. N., Arenal, R., Concepcion, P., Stach, E. A., & Corma, A. (2018). Evolution and stabilization of subnanometric metal species in confined space by in situ TEM. Nature Communications, 9(1). doi:10.1038/s41467-018-03012-6Yan, W., Xi, S., Du, Y., Schreyer, M. K., Tan, S. X., Liu, Y., & Borgna, A. (2018). Heteroatomic Zn-MWW Zeolite Developed for Catalytic Dehydrogenation Reactions: A Combined Experimental and DFT Study. ChemCatChem, 10(14), 3078-3085. doi:10.1002/cctc.201800199De Graaf, J., van Dillen, A. ., de Jong, K. ., & Koningsberger, D. . (2001). 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Acurácia do Timed Up and Go Test para rastrear risco de quedas em idosos da comunidade

Objective: To determine the accuracy of the Timed Up and Go Test (TUGT) for screening the risk of falls among community-dwelling elderly individuals. Method: This is a prospective cohort study with a randomly by lots without reposition sample stratified by proportional partition in relation to gender involving 63 community-dwelling elderly individuals. Elderly individuals who reported having Parkinson's disease, a history of transitory ischemic attack, stroke and with a Mini Mental State Exam lower than the expected for the education level, were on a wheelchair and that reported a single fall in the previous six months were excluded. The TUGT, a mobility test, was the measure of interested and the occurrence of falls was the outcome. The performance of basic activities of daily living (ADL) and instrumental activities of daily living (IADL) was determined through the Older American Resources and Services, and the socio-demographic and clinical data were determined through the use of additional questionnaires. Receiver Operating Characteristic Curves were used to analyze the sensitivity and specificity of the TUGT. Results: Elderly individuals who fell had greater difficulties in ADL and IADL (p&lt;0.01) and a slower performance on the TUGT (p=0.02). No differences were found in socio-demographic and clinical characteristics between fallers and non- fallers. Considering the different sensitivity and specificity, the best predictive value for discriminating elderly individuals who fell was 12.47 seconds [(RR= 3.2) 95% CI: 1.3- 7.7]. Conclusions: The TUGT proved to be an accurate measure for screening the risk of falls among elderly individuals. Although different from that reported in the international literature, the 12.47 second cutoff point seems to be a better predictive value for Brazilian elderly individuals.OBJETIVO: Determinar a acurácia do Timed Up and Go Test (TUGT) para rastrear risco de quedas em idosos da comunidade. \ud MÉTODO: Trata-se de um estudo de coorte prospectivo com amostra sorteada aleatoriamente, sem reposição e estratificada por partilha proporcional em relação ao sexo de 63 idosos da comunidade. Excluíram-se idosos com doença de Parkinson, ataque isquêmico transitório, acidente vascular encefálico, Miniexame do Estado Mental inferior ao considerado normal de acordo com a escolaridade, movimentação exclusiva por cadeira de rodas e relato de uma queda nos seis meses anteriores à primeira entrevista. O TUGT, um teste de mobilidade, foi a medida testada, e o desfecho, a ocorrência de queda. Mensuraram-se atividades básicas (ABVD) e instrumentais de vida diária (AIVD) pela Older American Resources and Services e dados sociodemográficos e clínicos por questionário complementar. Para analisar a sensibilidade e a especificidade do TUGT, utilizou-se a Receiver Operating Characteristic Curves (ROC). \ud RESULTADOS: Os idosos que caíram tinham maior dificuldade na execução de ABVD e AIVD (p<0,01) e desempenho mais lento no TUGT (p=0,02). Quanto às características sociodemográficas e clínicas, não houve diferença entre idosos que caíram e os que não caíram. Considerando as diferentes sensibilidades, especificidades e razões de verossimilhança, o melhor valor preditivo para discriminar idosos que caíram foi 12,47 segundos [(RR=3,2) IC95%: 1,3-7,7]. CONCLUSÃO: O TUGT é acurado para rastrear risco de quedas em idosos. O cut-off de 12,47 segundos, embora diferente da literatura internacional, parece ser um melhor valor preditivo para idosos brasileiros

MOF-mediated synthesis of supported Fe-doped Pd nanoparticles under mild conditions for magnetically recoverable catalysis

Metal-organic framework (MOF)-driven synthesis is considered as a promising alternative for the development of new catalytic materials with well-designed active sites. This synthetic approach is used here to gradually transform a new bimetallic MOF, with Pd and Fe as the metal components, by the in situ generation of aniline under mild conditions. This methodology results in a compositionally homogeneous nanocomposite formed by Fe-doped Pd nanoparticles that, in turn, are supported on iron oxide-doped carbon. The nanocomposite has been fully characterized by several techniques such as IR and Raman spectroscopy, TEM, XPS, and XAS. The performance of this nanocomposite as an heterogeneous catalyst for hydrogenation of nitroarenes and nitrobenzene coupling with benzaldehyde has been evaluated, proving it to be an efficient and reusable catalyst

Determination of the evolution of heterogeneous single metal atoms and nanoclusters under reaction conditions: Which are the working catalytic sites?

Identification of active sites in heterogeneous metal catalysts is critical for understanding the reaction mechanism at the molecular level and for designing more efficient catalysts. Because of their structural flexibility, subnanometric metal catalysts, including single atoms and clusters with a few atoms, can exhibit dynamic structural evolution when interacting with substrate molecules, making it difficult to determine the catalytically active sites. In this work, Pt catalysts containing selected types of Pt entities (from single atoms to clusters and nanoparticles) have been prepared, and their evolution has been followed, while they were reacting in a variety of heterogeneous catalytic reactions, including selective hydrogenation reactions, CO oxidation, dehydrogenation of propane, and photocatalytic H2 evolution reaction. By in situ X-ray absorption spectroscopy, in situ IR spectroscopy, and high-resolution electron microscopy techniques, we will show that some characterization techniques carried out in an inadequate way can introduce confusion on the interpretation of coordination environment of highly dispersed Pt species. Finally, the combination of catalytic reactivity and in situ characterization techniques shows that, depending on the catalyst–reactant interaction and metal–support interaction, singly dispersed metal atoms can rapidly evolve into metal clusters or nanoparticles, being the working active sites for those abovementioned heterogeneous reactions.This work has been supported by the European Union through the European Research Council (grant ERC-AdG-2014-671093, SynCatMatch) and the Spanish government through the “Severo Ochoa Program” (SEV-2016-0683). L.L. thanks ITQ for providing a contract. The authors also thank Microscopy Service of UPV for the TEM and STEM measurements. This research used resources of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, and was supported by the U.S. DOE under contract no. DE-AC02-06CH11357 and the Canadian Light Source and its funding partners. The HR STEM and STEM–EELS studies were conducted at the Laboratorio de Microscopias Avanzadas, Universidad de Zaragoza, Spain. R.A. acknowledges support from Spanish MINECO grant MAT2016-79776-P (AEI/FEDER, UE), from the Government of Aragon and the European Social Fund (grant number E13_17R, FEDER, UE), and from the European Union H2020 program “ESTEEM3” (grant number 823717). A.V.P. thanks the Spanish Government (Agencia Estatal de Investigación) and the European Union (European Regional Development Fund) for a grant for young researchers (CTQ2015-74138-JIN, AEI/FEDER/UE).Peer reviewe

Effect of the Pt precursor and loading on the structural parameters and catalytic properties of Pt/Al2O3

The effects of promoters and additives on the electronic properties and structural properties of Pt catalysts still need to be understood. The present work investigates the effects of the Pt loading and the use of chloride additive on the structural properties of Pt/Al2O3 and its catalytic activity towards the WGS reaction. The presence of Cl affected the morphology and oxygen coverage of the Pt nanoparticles. However, these parameters did not affect the surface electronic properties, due to a compensation effect between the size of the Pt-0 core and oxygen coordinated on the shell (NPt-O). Despite the structural differences, the catalytic activity for the WGS reaction was similar for the chloride-free sample and the catalyst containing chloride. The effect of the Pt loading was also studied, with the "apparent" catalytic activity per site of Pt (TOF) decreasing with increasing metal loading. Increasing the Pt loading led to an increase of the low-coordination Pt-0 sites at the surface of the NPs, resulting in stronger Pt-CO integration and consequent poisoning of the active sites111330643074CNPQ - Conselho Nacional de Desenvolvimento Científico e TecnológicoFAPESP – Fundação de Amparo à Pesquisa Do Estado De São PauloLNLS - Laboratório Nacional de Luz Síncrotron2011/50727-9; 2010/11385-2; 2016/02128-2; 2012/00567-8407030/2013-1sem informaçã

Structure and reactive properties of Nb-impregnated two-dimensional pillared MWW zeolites for total oxidation of volatile organic compounds

In this work, the structure and reactive properties of niobium (Nb)-impregnated MWW-type materials were evaluated for gas-phase total oxidation of volatile organic compounds, including BTX (benzene, toluene and o -xylene). The role of the type of structure (two or three-dimensional) and the loading of Nb were considered. The results indicated most Nb species with a tetrahedral coordination on the external surfaces of both two- and three-dimensional zeolites, together with a minimal contribution of octahedral extra-framework NbO species. The texture and Nb content played a key role in the gas-phase total oxidation of BTX. With the same Nb content (5 wt%), the pillared zeolite exhibited a higher specific surface, larger pore volume and mesopores between the MWW nanosheets when compared to the MCM-22 zeolites, which resulted in high accessibility of the reactant molecules to the active sites, reflected in higher BTX conversion at lower and higher temperatures (50–300 °C). The best performance was achieved with the pillared zeolite (10 wt% Nb), reaching a BTX conversion at 300 °C of 92%, 69% and 58%, respectively. The catalyst was stable for up to 30 h of reaction.A.J.S. thanks the Cordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Brazil; Finance Code 001) and the Programa de Pós-Graduação em Química of the Universidade Federal do Rio Grande do Sul (PPGQ-UFRGS). C.W.L. thanks the PRH 50.1 – ANP/FINEP Human Resources Program for the Visiting Researcher Fellowship. This research used resources of the Advanced Photon Source, a user facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, and was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357 and by the Canadian Light Source and its funding partners. U.D thanks the MAT2017-82288-C2-1-P Project.Peer reviewe

MOF-Mediated Synthesis of Supported Fe-doped Pd Nanoparticles under Mild Conditions for Magnetically Recoverable Catalysis

MOF-driven synthesis is considered as a promising alternative for the development of new catalytic materials with well-designed active sites. This synthetic approach is used here to gradually transform a new bimetallic MOF, composed of Pd and Fe as metal components, via the in situ generation of aniline under mild conditions. This methodology results in a compositionally homogeneous nanocomposite formed by Fedoped Pd nanoparticles and these, in turn, supported on an iron oxide-doped carbon. The nanocomposite has been fully characterized by several techniques such as IR, Raman, TEM, XPS, XAS, among others. The performance of this nanocomposite as an heterogeneous catalyst for hydrogenation of nitroarenes and nitrobenzene coupling with benzaldehyde has been evaluated, proving it to be an efficient and reusable catalyst

Structure-function relationship during CO2 methanation over Rh/Al2O3 and Rh/SiO2 catalysts under atmospheric pressure conditions

The effect of the support material and chemical state of Rh in Rh/A2O3 and Rh/SiO2 model catalysts during CO2 hydrogenation were studied by a combined array of in situ characterisation techniques including diffuse reflectance infrared Fourier transform spectroscopy, energy-dispersive X-ray absorption spectroscopy and high-energy X-ray diffraction at 250-350 °C and atmospheric pressure. CO2 methanation proceeds via intermediate formation of adsorbed CO species on metallic Rh, likely followed by their hydrogenation to methane. The linearly-bonded CO species is suggested to be a more active precursor in the hydrogenation compared to the bridge-bonded species, which seems to be related to particle size effects: for larger particles mainly the formation of inactive bridge-bonded CO species takes place. Further, analysis of the chemical state of Rh under the reaction conditions reveal a minor formation of RhOx from dissociation of CO2, which is a consequence of the increased activity observed over the Rh/Al2O3 catalyst