Metal organic frameworks as catalysts in solvent-free or ionic liquid assisted conditions

[EN] Metal organic frameworks (MOFs) are being intensively studied as solid catalysts for organic reactions in liquid media. This review focuses on those reports in which these materials have been used as catalysts in the absence of solvents or embedding ionic liquids (ILs). One of the major roles of solvents in liquid phase reactions is to desorb reagents and products from the active sites, facilitating the turnover of the active sites. For this reason, it is a general observation that most solid catalysts undergo strong deactivation and poisoning in the absence of solvents. In the present review, examples are presented showing that, due to their large porosity and framework flexibility, MOFs can be used as catalysts in the absence of solvents for several reaction types including cyanosilylations, condensations, cyloadditions and CO2 insertions, among others, and that they show even better performance than in the presence of conventional organic solvents. This review also describes the synergy that arises from the combination of ILs, frequently with suitable task-specific chains, and MOFs due to the cooperation with the catalysis when two centres in MOF and ionic liquid are present and due to the change in the microenvironment of the active sites. By embedding an ionic liquid in the MOF pores or by synthesising the ionic liquid covalently attached to the ligand in satellite positions, reusable and efficient catalysts requiring the minimum amount of ionic liquid can be obtained. Both complementary strategies increase the greenness of MOFs as heterogeneous catalysts and have advantages from the environmental point of view. Finally, the last section describes the catalytic activity of hierarchical porous MOFs in some selected reactions.AD thanks the University Grants Commission (UGC), New Delhi, for the award of an Assistant Professorship under its Faculty Recharge Programme. 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Generating and optimizing the catalytic activity in UiO-66 for aerobic oxidation of alkenes by post-synthetic exchange Ti atoms combined with ligand substitution

[EN] The catalytic activity for the aerobic epoxidation of cyclooctene of UiO-66 has been introduced by post synthetic ion exchange of Zr4+ by Ti4+ at the nodes and the performance optimized by nitro substitution in the terephthalate ligand. In this way a TON value of 16,600 (1660 considering Zr + Ti content) was achieved, comparing favorably with the highest catalytic activity reported in homogeneous for the same reaction (10,000 for gamma-SiW10{(Fe3+(OH2)}(O-38(6-)). Kinetic studies have shown that the most likely reactive oxygen species involved in the oxidation is superoxide, with hydroxyl radicals also contributing to the reaction. UiO-66(Zr-5.4 Ti-0.6)-NO2 is stable under catalytic conditions, being used six times without any change in the conversion temporal profile and in the X-ray diffractogram. The scope of UiO-66(Zr-5.4 Ti-0.6)-NO2 promoted aerobic oxidation of alkenes was expanded by including smaller rings cycloalkenes, as well as acyclic and aryl conjugated alkenes. (C) 2018 Elsevier Inc. All rights reserved.Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa and CTQ2014-53292-R and CTQ2015-69563-CO2-14) is gratefully acknowledged. Generalidad Valenciana is also thanked for funding (Prometeo 2017/018). SN thanks financial support by the Fundacion Ramon Areces (XVIII Concurso Nacional para la Adjudicacion de Ayudas a la Investigacion en Ciencias de la Vida y de la Materia, 2016).Santiago-Portillo, A.; Navalón Oltra, S.; Alvaro Rodríguez, MM.; García Gómez, H. (2018). Generating and optimizing the catalytic activity in UiO-66 for aerobic oxidation of alkenes by post-synthetic exchange Ti atoms combined with ligand substitution. Journal of Catalysis. 365:450-463. https://doi.org/10.1016/j.jcat.2018.07.032S45046336

General aspects in the use of graphenes in catalysis

[EN] This perspective is aimed at presenting some issues that, in our opinion, have still to be better addressed in the field of graphenes as catalysts. After an introductory section, the article comments on how the number of layers present on the catalyst, termed frequently as graphene, could be in some cases in contradiction with good practices about what should be or not considered as graphene. It will also be commented that some of the characterization tools that are employed in some cases for graphenes as catalysts, like specific surface area measurements based on isothermal gas adsorption on powders or XRD patterns are not well suited to characterizing graphenes. The potential role of impurities and structural defects in graphene catalysis has been highlighted showing the importance of providing exhaustive analysis of the materials. This perspective includes a final section with our view on future progress and wider consensus in the use of graphene in catalysis.Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa and CTQ2014-53292-R) is gratefully acknowledged. Generalidad Valenciana is also thanked for funding (Prometeo 2013/014). SN is thankful for financial support by the Fundacion Ramon Areces (XVIII Concurso Nacional para la Adjudicacion de Ayudas a la Investigacion en Ciencias de la Vida y de la Materia, 2016). Financial support by Fundacion Ramon Areces (XVII Concurso Nacional para la adjudicacion de Ayudas a la Investigacion en Ciencias de la Vida y de la Materia).Navalón Oltra, S.; Herance, JR.; Alvaro Rodríguez, MM.; García Gómez, H. (2018). General aspects in the use of graphenes in catalysis. Materials Horizons (Online). 5(3):363-378. https://doi.org/10.1039/c8mh00066bS3633785

Tuning the Microenvironment of Gold Nanoparticles Encapsulated within MIL-101(Cr) for the Selective Oxidation of Alcohols with O-2: Influence of the Amino Terephthalate Linker

This is the peer reviewed version of the following article: Chem. Eur. J. 2019, 25, 9280 9286, which has been published in final form at https://doi.org/10.1002/chem.201901361. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.[EN] This manuscript reports a comparative study of the catalytic performance of gold nanoparticles (NPs) encapsulated within MIL-101(Cr) with or without amino groups in the terephthalate linker. The purpose is to show how the amino groups can influence the microenvironment and catalytic stability of incorporated gold nanoparticles. The first influence of the presence of this substituent is the smaller particle size of Au NPs hosted in MIL-101(Cr)-NH2 (2.45 +/- 0.19 nm) compared with the parent MIL-101(Cr)-H (3.02 +/- 0.39 nm). Both materials are highly active to promote the aerobic alcohol oxidation and exhibit a wide substrate scope. Although both catalysts can achieve turnover numbers as high as 10(6) for the solvent-free aerobic oxidation of benzyl alcohol, Au@MIL-101(Cr)-NH2 exhibits higher turnover frequency values (12 000 h(-1)) than Au@MIL-101(Cr)-H (6800 h(-1)). Au@MIL-101(Cr)-NH2 also exhibits higher catalytic stability, being recyclable for 20 times with coincident temporal conversion profiles, in comparison with some decay observed in the parent Au@MIL-101(Cr)-H. Characterization by transmission electron microscopy of the 20-times used samples shows a very minor particle size increase in the case of Au@MIL-101(Cr)-NH2 (2.97 +/- 0.27 nm) in comparison with the Au@MIL-101(Cr)-H analog (5.32 +/- 0.72 nm). The data presented show the potential of better control of the microenvironment to improve the performance of encapsulated Au nanoparticles.Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa, CTQ2015-65963-CQ-R1 and CTQ2014-53292-R) is gratefully acknowledged. Generalidad Valenciana is also thanked for funding (Prometeo 2017/083). S.N. thanks financial support by the Fundacijn Ramjn Areces (XVIII Concurso Nacional para la Adjudicacijn de Ayudas a la Investigacijn en Ciencias de la Vida y de la Materia, 2016).Santiago-Portillo, A.; Cabrero-Antonino, M.; Alvaro Rodríguez, MM.; Navalón Oltra, S.; García Gómez, H. (2019). Tuning the Microenvironment of Gold Nanoparticles Encapsulated within MIL-101(Cr) for the Selective Oxidation of Alcohols with O-2: Influence of the Amino Terephthalate Linker. Chemistry - A European Journal. 25(39):9280-9286. https://doi.org/10.1002/chem.201901361S928092862539H�ft, E., Kosslick, H., Fricke, R., & Hamann, H.-J. (1996). Titanhaltige Molekularsiebe als Katalysatoren f�r selektive Oxidationsreaktionen mit Wasserstoffperoxid. Journal f�r Praktische Chemie/Chemiker-Zeitung, 338(1), 1-15. doi:10.1002/prac.19963380102Matsumoto, T., Ueno, M., Wang, N., & Kobayashi, S. (2008). Recent Advances in Immobilized Metal Catalysts for Environmentally Benign Oxidation of Alcohols. Chemistry - An Asian Journal, 3(2), 196-214. doi:10.1002/asia.200700359Saikia, M., Bhuyan, D., & Saikia, L. (2015). Facile synthesis of Fe3O4nanoparticles on metal organic framework MIL-101(Cr): characterization and catalytic activity. New Journal of Chemistry, 39(1), 64-67. doi:10.1039/c4nj01312cCorma, A., & Garcia, H. (2008). Supported gold nanoparticles as catalysts for organic reactions. Chemical Society Reviews, 37(9), 2096. doi:10.1039/b707314nParmeggiani, C., & Cardona, F. (2012). Transition metal based catalysts in the aerobic oxidation of alcohols. Green Chemistry, 14(3), 547. doi:10.1039/c2gc16344fStahl, S. S. (2004). Palladium Oxidase Catalysis: Selective Oxidation of Organic Chemicals by Direct Dioxygen-Coupled Turnover. Angewandte Chemie International Edition, 43(26), 3400-3420. doi:10.1002/anie.200300630Dhakshinamoorthy, A., & Garcia, H. (2012). Catalysis by metal nanoparticles embedded on metal–organic frameworks. Chemical Society Reviews, 41(15), 5262. doi:10.1039/c2cs35047eAlhumaimess, M., Lin, Z., He, Q., Lu, L., Dimitratos, N., Dummer, N. F., … Hutchings, G. J. (2014). Oxidation of Benzyl Alcohol and Carbon Monoxide Using Gold Nanoparticles Supported on MnO2Nanowire Microspheres. Chemistry - A European Journal, 20(6), 1701-1710. doi:10.1002/chem.201303355Buonerba, A., Cuomo, C., Ortega Sánchez, S., Canton, P., & Grassi, A. (2011). Gold Nanoparticles Incarcerated in Nanoporous Syndiotactic Polystyrene Matrices as New and Efficient Catalysts for Alcohol Oxidations. Chemistry - A European Journal, 18(2), 709-715. doi:10.1002/chem.201101034Costa, V. V., Estrada, M., Demidova, Y., Prosvirin, I., Kriventsov, V., Cotta, R. F., … Gusevskaya, E. V. (2012). Gold nanoparticles supported on magnesium oxide as catalysts for the aerobic oxidation of alcohols under alkali-free conditions. 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(2016). Chemical, thermal and mechanical stabilities of metal–organic frameworks. Nature Reviews Materials, 1(3). doi:10.1038/natrevmats.2015.18Lee, J., Farha, O. K., Roberts, J., Scheidt, K. A., Nguyen, S. T., & Hupp, J. T. (2009). Metal–organic framework materials as catalysts. Chemical Society Reviews, 38(5), 1450. doi:10.1039/b807080fLeus, K., Concepcion, P., Vandichel, M., Meledina, M., Grirrane, A., Esquivel, D., … Van Der Voort, P. (2015). Au@UiO-66: a base free oxidation catalyst. RSC Advances, 5(29), 22334-22342. doi:10.1039/c4ra16800cSaikia, M., Kaichev, V., & Saikia, L. (2016). Gold nanoparticles supported on nanoscale amine-functionalized MIL-101(Cr) as a highly active catalyst for epoxidation of styrene. RSC Advances, 6(108), 106856-106865. doi:10.1039/c6ra24458kLiu, H., Liu, Y., Li, Y., Tang, Z., & Jiang, H. (2010). Metal−Organic Framework Supported Gold Nanoparticles as a Highly Active Heterogeneous Catalyst for Aerobic Oxidation of Alcohols. The Journal of Physical Chemistry C, 114(31), 13362-13369. doi:10.1021/jp105666fLammert, M., Bernt, S., Vermoortele, F., De Vos, D. E., & Stock, N. (2013). Single- and Mixed-Linker Cr-MIL-101 Derivatives: A High-Throughput Investigation. Inorganic Chemistry, 52(15), 8521-8528. doi:10.1021/ic4005328Zhu, Q.-L., Li, J., & Xu, Q. (2013). Immobilizing Metal Nanoparticles to Metal–Organic Frameworks with Size and Location Control for Optimizing Catalytic Performance. Journal of the American Chemical Society, 135(28), 10210-10213. doi:10.1021/ja403330mChen, Y. F., Babarao, R., Sandler, S. I., & Jiang, J. W. (2010). Metal−Organic Framework MIL-101 for Adsorption and Effect of Terminal Water Molecules: From Quantum Mechanics to Molecular Simulation. Langmuir, 26(11), 8743-8750. doi:10.1021/la904502hFerey, G. (2005). A Chromium Terephthalate-Based Solid with Unusually Large Pore Volumes and Surface Area. Science, 309(5743), 2040-2042. doi:10.1126/science.1116275Santiago-Portillo, A., Navalón, S., Cirujano, F. G., Xamena, F. X. L. i, Alvaro, M., & Garcia, H. (2015). MIL-101 as Reusable Solid Catalyst for Autoxidation of Benzylic Hydrocarbons in the Absence of Additional Oxidizing Reagents. ACS Catalysis, 5(6), 3216-3224. doi:10.1021/acscatal.5b00411Buxton, G. V., Greenstock, C. L., Helman, W. P., & Ross, A. B. (1988). Critical Review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals (⋅OH/⋅O− in Aqueous Solution. Journal of Physical and Chemical Reference Data, 17(2), 513-886. doi:10.1063/1.555805Clifton, C. L., & Huie, R. E. (1989). Rate constants for hydrogen abstraction reactions of the sulfate radical, SO4?. Alcohols. International Journal of Chemical Kinetics, 21(8), 677-687. doi:10.1002/kin.550210807Dhakshinamoorthy, A., Asiri, A. M., & Garcia, H. (2017). 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Nitro functionalized chromium terephthalate metal-organic framework as multifunctional solid acid for the synthesis of benzimidazoles

[EN] In the present work, nitro functionalized chromium terephthalate [MIL-101(Cr)-NO2] metal-organic framework is prepared and characterized by powder X-ray diffraction (XRD), elemental analysis, infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Brun auer-Emmett-Teller (BET) surface area. The inherent Lewis acidity of MIL-101(Cr)-NO2 is confirmed by FT-IR spectroscopy using CD3CN as a probe molecule. The performance of MIL-101(Cr)-NO2 as bifunctional catalyst (acid and redox) promoting the synthesis of wide range of benzimidazoles has been examined by catalyzed condensation on acid sites and subsequent oxidative dehydrogenation. The catalytic activity of MIL-101(Cr)-NO2 is found to be superior than analogues catalysts like MIL-101(Cr)-S0(3)H, MIL-101(Cr)-NH2, U10-66(Zr), Ui0-66(Zr)-NO2, MIL-100(Fe) and Cu-3(BTC)(2) (BTC: 1,35-benzenetricarboxylate) under identical reaction conditions, The structural stability of MIL-101(Cr)-NO2 is supported by leaching analysis and reusability tests. MIL-101(Cr)-NO2 solid is used five times without decay in its activity. Comparison of the fresh and five times used MIL-101(Cr)-NO2 solids by powder XRD, SEM and elemental analysis indicate identical crystallinity, morphology and the absence of chromium leaching, respectively. (C) 2019 Elsevier Inc. All rights reserved.AD thanks the University Grants Commission, New Delhi, for the award of an Assistant Professorship under its Faculty Recharge Programme. AD also thanks the Department of Science and Technology, India, for the financial support through Extra Mural Research Funding (EMR/2016/006500). Financial support by the Spanish Ministry of Science and Innovation (Severo Ochoa and RTI2018-098237-CO21) and Generalitat Valenciana (Prometeo 2017/083) is gratefully acknowledged. S.N. thanks financial support by the Fundacion Ramon Areces (XVIII Concurso Nacional para la Adjudication de Ayudas a la Investigacion en Ciencias de la Vida y de la Materia, 2016), Ministerio de Ciencia, Innovation y Universidades RTI2018-099482-A-I00 project and Generalitat Valenciana grupos de investigacion consolidables 2019 (AICO/2019/214) project.Vallés-García, C.; Cabrero-Antonino, M.; Navalón Oltra, S.; Alvaro Rodríguez, MM.; Dhakshinamoorthy, A.; García Gómez, H. (2020). Nitro functionalized chromium terephthalate metal-organic framework as multifunctional solid acid for the synthesis of benzimidazoles. 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CO2 cycloaddition of styrene oxide over MOF catalysts. Applied Catalysis A: General, 453, 175-180. doi:10.1016/j.apcata.2012.12.018Li, B., Leng, K., Zhang, Y., Dynes, J. J., Wang, J., Hu, Y., … Ma, S. (2015). Metal–Organic Framework Based upon the Synergy of a Brønsted Acid Framework and Lewis Acid Centers as a Highly Efficient Heterogeneous Catalyst for Fixed-Bed Reactions. Journal of the American Chemical Society, 137(12), 4243-4248. doi:10.1021/jacs.5b01352Mitchell, L., Gonzalez-Santiago, B., Mowat, J. P. S., Gunn, M. E., Williamson, P., Acerbi, N., … Wright, P. A. (2013). Remarkable Lewis acid catalytic performance of the scandium trimesate metal organic framework MIL-100(Sc) for C–C and CN bond-forming reactions. Catal. Sci. Technol., 3(3), 606-617. doi:10.1039/c2cy20577gBhattacharjee, S., Chen, C., & Ahn, W.-S. (2014). Chromium terephthalate metal–organic framework MIL-101: synthesis, functionalization, and applications for adsorption and catalysis. RSC Adv., 4(94), 52500-52525. doi:10.1039/c4ra11259hNiknam, E., Panahi, F., Daneshgar, F., Bahrami, F., & Khalafi-Nezhad, A. (2018). Metal–Organic Framework MIL-101(Cr) as an Efficient Heterogeneous Catalyst for Clean Synthesis of Benzoazoles. ACS Omega, 3(12), 17135-17144. doi:10.1021/acsomega.8b02309Darunte, L. A., Oetomo, A. D., Walton, K. S., Sholl, D. S., & Jones, C. W. (2016). Direct Air Capture of CO2 Using Amine Functionalized MIL-101(Cr). ACS Sustainable Chemistry & Engineering, 4(10), 5761-5768. doi:10.1021/acssuschemeng.6b01692Gao, L., Li, C.-Y. V., Yung, H., & Chan, K.-Y. (2013). A functionalized MIL-101(Cr) metal–organic framework for enhanced hydrogen release from ammonia borane at low temperature. Chemical Communications, 49(90), 10629. doi:10.1039/c3cc45719bHartmann, M., & Fischer, M. (2012). Amino-functionalized basic catalysts with MIL-101 structure. 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Highly fluorescent C-dots obtained by pyrolysis of quaternary ammonium ions trapped in all-silica ITQ-29 zeolite

[EN] C-dots obtained in the homogeneous phase may exhibit a broad particle size distribution. The formation of C-dots within nanometric reaction cavities could be a methodology to gain control on their size distribution. Among the various possibilities, in the present work, the cavities of small pore size zeolites have been used to confine C-dots generated by the pyrolysis of the organic structure directing agent present in the synthesis of these crystalline aluminosilicates. To explore this methodology, ITQ-29 zeolite having a Linde type A (LTA) structure was prepared as pure silica with 4-methyl-2,3,6,7-tetrahydro-1H, 5H-pyrido[3.2.1-ij] quinolinium as the organic structure directing agent. Pyrolysis under an inert atmosphere at 550 degrees C of a pure-silica ITQ-29 sample (cubic particles of 4 mu m edge) renders a highly fluorescent zeolite containing about 15 wt% of the carbonised residue. While another small pore zeolite, ITQ-12 (ITW), also renders photoluminescent C-dots under similar conditions, medium or large pore zeolites, such as silicalite (MFI) or pure silica Beta (BEA), failed to produce fluorescent powders under analogous thermal treatment and only decomposition and complete removal of the corresponding quaternary ammonium ion templates was observed for these zeolites. The dissolution of the pyrolysed ITQ-29 zeolite framework and the extraction of the carbon residue with ethyl acetate have allowed the characterisation of C-dots with particle sizes between 5 and 12 nm and a photoluminescence quantum yield of 0.4 upon excitation at 350 nm that is among the highest reported for non-surface functionalized C-dots. Photoluminescence varies with the excitation wavelength and is quenched by oxygen. Pyrolysed ITQ-29 powders can act as fluorescent oxygen sensors.Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa and CTQ2012-32315) and Generalidad Valenciana (Prometeo 2012-014) is gratefully acknowledged.García Baldoví, H.; Valencia Valencia, S.; Alvaro Rodríguez, MM.; Abdullah, AM.; García Gómez, H. (2015). Highly fluorescent C-dots obtained by pyrolysis of quaternary ammonium ions trapped in all-silica ITQ-29 zeolite. Nanoscale. 7(5):1744-1752. https://doi.org/10.1039/C4NR05295AS174417527

Engineering Active Sites in Reduced Graphene Oxide: Tuning the Catalytic Activity for Aerobic Oxidation

"This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Sustainable Chemistry & Engineering, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acssuschemeng.9b02237."[EN] The influence of the graphene oxide (GO) reduction method on the activity of the resulting reduced graphene oxide (rGO) for the aerobic oxidation of benzylamine is reported. Starting from GO obtained by the Hummers method, a series of rGO samples were obtained either by chemical (hydroquinone (HQ), hydrazine (HZ) or ascorbic acid (ASC)) or by thermal reduction were prepared. Analytical and spectroscopic techniques provide evidence showing that chemical reducing agents reduce GO with different functional groups that influence the catalytic activity of the resulting rGO for the activation of molecular oxygen in benzylamine oxidation. The highest activity in the aerobic oxidation of benzylamine at 80 degrees C was found for the rGO-HQ1 sample prepared using HQ as a reducing agent. It is proposed that HQ introduces hydroquinone/p-benzoquinone-like moieties on the graphene sheet that act as active sites in the oxidation reaction. This proposal is supported by the activity of HQand/or p-benzoquinone as organocatalysts and by selective masking of oxygen-functional groups present in the most active rGO sample. The most active rGO sample exhibited good reusability and stability in five consecutive uses. Selective quenching experiments revealed that hydroperoxyl radicals are the primary reactive oxygen species generated in the system.Financial support by the Spanish Ministry of Science and Innovation (Severo Ochoa and RTI2018-098237-CO21) and Generalitat Valenciana (Prometeo 2017/083) is gratefully acknowledged. S.N. thanks financial support by the Fundacion RamOn Areces (XVIII Concurso Nacional para la Adjudication de Ayudas a la Investigation en Ciencias de la Vida y de la Materia, 2016) and Ministerio de Ciencia, Innovation y Universidades RTI2018-099482-A-I00 project and Generalitat Valenciana (grupos de investigation consolidables 2019, AICO/2019/214). A.D. thanks the University Grants Commission, New Delhi, for the award of an Assistant Professorship under its Faculty Recharge Programme. A.D. also thanks the Department of Science and Technology, India, for the financial support through Extramural Research Funding (EMR/2016/006500).Espinosa-López, JC.; Alvaro Rodríguez, MM.; Dhakshinamoorthy, A.; Navalón Oltra, S.; García Gómez, H. (2019). Engineering Active Sites in Reduced Graphene Oxide: Tuning the Catalytic Activity for Aerobic Oxidation. ACS Sustainable Chemistry & Engineering. 7(19):15948-15956. https://doi.org/10.1021/acssuschemeng.9b02237S159481595671

MIL-101(Cr)-NO2 as efficient catalyst for the aerobic oxidation of thiophenols and the oxidative desulfurization of dibenzothiophenes

[EN] A series of MIL-101(Cr)-X functionalized with electron withdrawing (NO2, SO3H or Cl) or electron donor (NH2 or CH3) groups has been tested for the solvent-free oxidative coupling of thiophenol to disulfides. No byproducts were observed. A relationship between the catalytic activity of these MOFs with the substituent meta Hammet constant on the terephthalate ligand and with their redox potential was found, MIL-101(Cr)-NO2 being the most active catalyst. NO2-substituted MIL-101 is also more efficient than the parent MIL-101(Cr) to promote the aerobic desulfurization of dibenzothiophenes in n-dodecane or commercial Diesel as solvent. No byproduct formation was observed. Mechanistic studies reveal that MIL-101(Cr)-NO2 is acting as heterogeneous catalyst in thiophenol oxidation and as radical initiator for the aerobic desulfurization. For both reactions, the catalyst can be reused without deactivation, maintaining its crystallinity and with negligible metal leaching.Financial support by the Spanish Ministry of Science and Innovation (Severo Ochoa and RTI2018-098237-CO21) and Generalitat Valenciana (Prometeo 2017/083) is gratefully acknowledged. S.N. thanks financial support by the Fundacion Ramon Areces (XVIII Concurso Nacional para la Adjudicacion de Ayudas a la Investigacion en Ciencias de la Vida y de la Materia, 2016), Ministerio de Ciencia, Innovacion y Universidades CTQ-2018 RTI2018-099482-A-I00 project and Generalitat Valenciana grupos de investigacion consolidables 2019 (AICO2019/214 project).Vallés-García, C.; Santiago-Portillo, A.; Alvaro Rodríguez, MM.; Navalón Oltra, S.; García Gómez, H. (2020). MIL-101(Cr)-NO2 as efficient catalyst for the aerobic oxidation of thiophenols and the oxidative desulfurization of dibenzothiophenes. 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Influence of the organic linker substituent on the catalytic activity of MIL-101(Cr) for the oxidative coupling of benzylamines to imines

[EN] MIL-101(Cr) having substituents at the terephthalate linker (X = H, NO2, SO3H, Cl, CH3 and NH2) promotes the aerobic oxidation of benzylamines to the corresponding N-benzylidene benzylamines at different rates. MIL-101(Cr)¿NO2 was the most active catalyst, about 6-fold more active than the parent MIL-101(Cr). MIL-101(Cr)¿NO2 does not deactivate significantly upon five consecutive reuses, does not leach the metal to the solution and maintains its crystallinity. MIL-101(Cr)¿NO2 is active for a wide range of benzylamines including para-substituted, heterocyclic benzylamines and di- and tribenzylamines.Financial support by the Spanish Ministry of Economy and Competitiveness (CTQ 2015-69153-CO2-1, CTQ2014-53292-R, Severo Ochoa) and Generalitat Valenciana (Prometeo 2013014) is gratefully acknowledged.Santiago-Portillo, A.; Blandez, JF.; Navalón Oltra, S.; Alvaro Rodríguez, MM.; García Gómez, H. (2017). Influence of the organic linker substituent on the catalytic activity of MIL-101(Cr) for the oxidative coupling of benzylamines to imines. Catalysis Science & Technology. 7(6):1351-1362. https://doi.org/10.1039/c6cy02577cS135113627

Influence of radical initiators in gold catalysis: Evidence supporting trapping of radicals derived from azobis(isobutyronitrile) by gold halides

[EN] Gold halides (AuCl3, HAuCl4, and AuCl) efficiently trap the radicals generated in the room-temperature photolysis of azobis(isobutyronitrile) (AIBN) to give an organogold H[(CH3)(2)CCN](2)AuCl2 compound that has been characterized by spectroscopy. The characteristic features of the organogold are a quaternary carbon at 100 ppm on C-13 NMR and a HR-MS peak with a molecular formula Of C8H13N2AuCl. Catalytic data for cyclohexene aerobic oxidation confirms the beneficial influence of the presence of AlBN on the catalytic activity of Au/CeO2C.Alvaro Rodríguez, MM.; Aprile ., C.; Corma Canós, A.; Ferrer Ribera, RB.; García Gómez, H. (2006). Influence of radical initiators in gold catalysis: Evidence supporting trapping of radicals derived from azobis(isobutyronitrile) by gold halides. Journal of Catalysis. 245(1):249-252. doi:10.1016/j.jcat.2006.10.003S249252245