Cobalt-Based Metal Organic Frameworks as Solids Catalysts for Oxidation Reactions

[EN] Metal organic frameworks (MOFs) are porous crystalline solids whose frameworks are constituted by metal ions/nodes with rigid organic linkers leading to the formation of materials having high surface area and pore volume. One of the unique features of MOFs is the presence of coordinatively unsaturated metal sites in their crystalline lattice that can act as Lewis acid sites promoting organic transformations, including aerobic oxidation reactions of various substrates such as hydrocarbons, alcohols, and sulfides. This review article summarizes the existing Co-based MOFs for oxidation reactions organized according to the nature of substrates like hydrocarbon, alcohol, olefin, and water. Both aerobic conditions and peroxide oxidants are discussed. Emphasis is placed on comparing the advantages of using MOFs as solid catalysts with respect to homogeneous salts in terms of product selectivity and long-term stability. The final section provides our view on future developments in this field.H.G. is thankful for financial assistance from the Spanish Ministry of Science and Innovation (Severo Ochoa and CTQ2018-980237-CO2-1) and Generalitat Valenciana (Prometeo 2017-083). A.D. is thankful for the University Grants Commission, New Delhi, for awarding an Assistant Professorship through the Faculty Recharge Programme. A.D. acknowledges financial assistance from the Science Engineering Research Board, India, through its Extra Mural Research project (EMR/2016/006500). S.N. is thankful for financial support by the Ministerio de Ciencia, Innovacion y Universidades (RTI 2018-099482-A-I00 project), Fundacion Ramon Areces (XVIII Concurso Nacional para la Adjudicacion de Ayudas a la Investigacion en Ciencias de la Vida y de la Materia, 2016) and Agencia Valenciana de la Innovacion (AVI-GVA, Carboagua project, INNEST/2020/111).Dhakshinamoorthy, A.; Montero-Lanzuela, E.; Navalón Oltra, S.; García Gómez, H. (2021). Cobalt-Based Metal Organic Frameworks as Solids Catalysts for Oxidation Reactions. Catalysts. 11(1):1-25. https://doi.org/10.3390/catal1101009512511

A Novel Porous Ti-Squarate as Efficient Photocatalyst in the Overall Water Splitting Reaction under Simulated Sunlight Irradiation

[EN] A new porous titanium(IV) squarate metal¿organic framework (MOF), denoted as IEF-11, having a never reported titanium secondary building unit, is successfully synthesized and fully characterized. IEF-11 not only exhibits a permanent porosity but also an outstanding chemical stability. Further, as a consequence of combining the photoactive Ti(IV) and the electroactive squarate, IEF-11 presents relevant optoelectronic properties, applied here to the photocatalytic overall water splitting reaction. Remarkably, IEF-11 as a photocatalyst is able to produce record H2 amounts for MOF-based materials under simulated sunlight (up to 672 µmol gcatalyst in 22 h) without any activity loss during at least 10 d.P.S.-A. and A.A.B. contributed equally to this work. The authors acknowledge the Ramón Areces Foundation project H+MOFs, the M-ERA-NET C-MOF-cell (grant PCI2020-111998 funded by MCIN/AEI/10.13039/501100011033 and European Union NextGenerationEU/ PRTR) project, and Retos Investigación MOFSEIDON (grant PID2019-104228RB-I00 funded by MCIN/AEI/10.13039/501100011033) project. S.N. thanks financial support by Ministerio de Ciencia, Innovatión y Universidades RTI2018-099482-A-I00 project and Agència Valenciana de la Innovació (AVI, INNEST/2020/111) project. H.G. thanks financial support to the Spanish Ministry of Science and Innovation (Severo Ochoa and RTI2018-098237-CO21) and Generalitat Valenciana (Prometeo2017/083). T.W. acknowledges financial support from the Swedish Research Council (VR, 2019-05465). Parts of this research were carried out at ¿CRISTAL¿ at SOLEIL. P.S. and A.A.B. sincerely thank to the project CALIPSOplus under the Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020 for the support of the synchrotron experiment.Salcedo-Abraira, P.; Babaryk, AA.; Montero-Lanzuela, E.; Contreras Almengor, OR.; Cabrero-Antonino, M.; Svensson, E.; Willhammar, T.... (2021). A Novel Porous Ti-Squarate as Efficient Photocatalyst in the Overall Water Splitting Reaction under Simulated Sunlight Irradiation. Advanced Materials. 33(52):1-9. https://doi.org/10.1002/adma.20210662719335

Estudio de la actividad catalítica de materiales basados en grafito para la desulfuración aeróbica oxidativa de fracciones del petróleo destinadas a la producción de combustibles de automoción

[ES] En la actualidad, existe una legislación ambiental muy estricta con respecto al contenido de azufre que pueden contener los combustibles de automoción. La presencia de compuestos de azufre en los combustibles da lugar a la generación de óxidos de azufre y posterior formación de lluvia ácida. Estos hechos producen impactos negativos para el medioambiente y para la salud humana que son necesarios minimizar. Según la directiva 2003/17/CE, desarrollada en el Real Decreto 61/2006, de 31 de enero, el contenido máximo permitido de azufre en gasolina y diésel es de 10 mg¿Kg-1. El método tradicional de desulfuración de fracciones del petróleo destinadas a la producción de combustibles es conocido como hidrodesulfuración. Sin embargo, este método no es eficiente para llevar a cabo la desulfuración de fracciones destinadas a la producción de diésel o gasolina, que presentan un elevado contenido en compuestos organosulfurados como los dibenzotiofenos. En este sentido, la desulfuración oxidativa es una de las alternativas más prometedoras para superar las dificultades de la hidrodesulfuración convencional. El proceso consiste en llevar a cabo la oxidación catalítica de los compuestos organosulfurados a los correspondientes sulfóxidos y/o sulfonas, que son separados en una segunda etapa del combustible. En general, el proceso de oxidación está catalizado por metales de transición en presencia de peróxidos o hidroperóxidos que actúan como agentes oxidantes. En el presente trabajo fin de grado se han empleado materiales basados en grafito como carbocatalizadores para llevar a cabo el proceso de desulfuración oxidativa, empleando oxígeno molecular como agente oxidante. El empleo de un grafito de alta área superficial ha resultado ser el carbocatalizador más activo para llevar a cabo este proceso. La actividad catalítica de este catalizador es mucho mayor que la obtenida empleando catalizadores análogos basados en carbón activo. El proceso de desulfuración aeróbico oxidativo empleando grafito de alta área superficial como carbocatalizador y oxígeno como oxidante acoplado con un sistema de extracción líquido-líquido empleando agua como disolvente permite reducir el contenido en azufre por debajo de los límites establecidos por la normativa (< 10 mg¿Kg-1 S).[EN] At present, there is a very strict environmental legislation regarding the sulfur content that automotive fuels can contain. The presence of sulfur compounds in fuels leads to the generation of sulfur oxides and subsequent formation of acid rain. These facts produce negative impacts for the environment and for human health that must be minimized. According to directive 2003/17 / EC, developed in Royal Decree 61/2006, of January 31, the maximum allowed sulfur content in gasoline and diesel is 10 mg¿Kg-1. The traditional method of desulfurization of fractions of petroleum destined to the production of fuels is known as hydrodesulfurization. However, this method is not efficient to carry out the desulfurization of fractions destined to the production of diesel or gasoline which have a high content of organosulfur compounds such as dibenzothiophenes. In this sense, oxidative desulfurization is one of the most promising alternatives to overcome the difficulties of conventional hydrodesulfurization. This process consists in carrying out the catalytic oxidation of the organosulfur compounds to the corresponding sulfoxides and/or sulfones which are separated in a second fuel stage. In general, the oxidation process is catalyzed by transition metals in the presence of peroxides or hydroperoxides that act as oxidizing agents. In this end-of-degree project, graphite-based materials have been used as carbocatalysts to carry out the oxidative desulphurization process using oxygen molecular as an oxidizing agent. High surface area graphite has been the most active carbocatalyst to carry out this process. The catalytic activity of this catalyst is higher than that obtained by using analogous catalysts based on active carbon. The process of oxidative aerobic desulfurization using high surface graphite as a carbocatalyst and oxygen as an oxidant coupled with a liquid-liquid extraction system using water as a solvent allows to reduce the sulfur content below the limits established by the regulations (<10 m¿Kg-1 S).Montero Lanzuela, E. (2018). Estudio de la actividad catalítica de materiales basados en grafito para la desulfuración aeróbica oxidativa de fracciones del petróleo destinadas a la producción de combustibles de automoción. http://hdl.handle.net/10251/108328TFG

Room Temperature design of Ce(IV)-MOFs: from photocatalytic HER and OER to overall water splitting under simulated sunlight irradiation

Room temperature synthesis (RTS) of tetravalent MOFs is a promising strategy to design MOFs and their related (nano)composites. By employing these mild conditions, herein, we report for the first time an efficient sustainable way to form highly redox active Ce(IV)-MOFs that are inaccessible at elevated temperatures. Consequently, not only highly crystalline Ce-UiO-66-NH2 is synthesized, but also many other derivatives and topologies (8 and 6-connected phases) without compromise in space-time yield. Their photocatalytic HER and OER activity under simulated sunlight irradiation are in good agreement with their energy level diagrams: Ce-UiO-66-NH2 and Ce-UiO-66-NO2 are the most active photocatalysts for the HER and OER, respectively, with a higher activity than other metals-based UiO-type MOFs. Combining Ce-UiO-66-NH2 with supported Pt NPs results finally in one of the most active and reusable photocatalysts for the overall water splitting into H2 and O2 under simulated sunlight irradiation, due to its efficient photoinduced charge separation evidenced by laser flash photolysis and photoluminescence spectroscopies

Tuning the active sites in reduced graphene oxide by hydroquinone functionalization for the aerobic oxidations of thiophenol and indane

[EN] Sustainable reduced graphene oxide (rGO) carbocatalysts for molecular oxygen activation have been developed based on the concept that chemical reduction of graphene oxide to rGO introduces functional groups that can become active sites. Thus, a series of rGOs prepared using hydroquinone (HQ), hydrazine (HZ) and ascorbic acid (ASC) as reducing agents have been tested as catalysts in the aerobic oxidations of thiophenol and indane. In both oxidation reactions, rGO reduced by HQ (rGO-HQ) exhibited the highest catalytic activity and stability. A high selectivity of of/one (90 %) at around 30 % indane conversion in the absence of transition metals was achieved. Reusability test showed that the activity of rGO-HQ is mostly retained in three consecutive runs. Quenching experiments indicated that the reaction proceeds with the generation of hydroxyl and carbon centered radicals. The higher activity of rGO-HQ was attributed to the covalent anchoring of some HQ molecules on rGO during the chemical reduction. This knowledge has been used to develop a HQ-functionalized Merrifield resin that in spite of its very different textural properties compared to rGO also exhibits catalytic activity for O-2 activation. The present work illustrates the potential to develop rGO carbocatalysts with an increased density of active sites by selecting an appropriate reducing agent during the chemical reduction of graphene oxide.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 UniversidadesRTI2018-099482-A-I00 project and Generalitat Valenciana grupos de investigacion consolidables 2019 (ref: AICO/2019/214) project. 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). Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa and RTI2018-089231-CO2-R1) and Generalitat Valenciana (Prometeo 2017-083) is gratefully acknowledged.Vallés-García, C.; Montero-Lanzuela, E.; Navalón Oltra, S.; Alvaro Rodríguez, MM.; Dhakshinamoorthy, A.; García Gómez, H. (2020). Tuning the active sites in reduced graphene oxide by hydroquinone functionalization for the aerobic oxidations of thiophenol and indane. Molecular Catalysis. 493:1-7. https://doi.org/10.1016/j.mcat.2020.111093S1749

Hybrid sp2/sp3 nanodiamonds as heterogeneous metal-free ozonation catalysts in water

[EN] There is a growing interest from academia and industry in metal-free heterogeneous catalysts as an alternative to current non-sustainable transition metal catalysts. Herein we report a comprehensive study on the development of hybrid nanodiamonds with a diamond core and defective graphitic shells with different sp2/sp3 ratios as metal-free ozonation catalysts. A volcano-type trend relationship between the catalytic activities with respect to the sp2/sp3 ratio was found. The most active nanodiamond pyrolysed at 1100 degrees C for 1 h exhibits a unique sp2/sp3 configuration together with an optimum amount of oxygen and nitrogen functional groups. O3 is catalytically transformed into hydroperoxyl radicals and 1O2 species. The catalytic activity of the spent hybrid nanodiamonds can be recovered by a simple annealing in an inert atmosphere that reconstitutes the defective sp2/sp3 hybrid nanodiamond. This study exemplifies the possibility of tailoring the physico-chemical properties of commercial nanodiamonds for the development of active metal-free ozonation catalysts.E.M.L. acknowledges the Generalitat Valenciana for a Ph.D. grant (ACIF/2020/267). S.N. thanks financial support by Ministerio de Ciencia, Innovati on y Universidades RTI2018-099482-A-I00 project and Agència Valenciana de la Innovació (AVI, INNEST/2020/111) project.Bernat-Quesada, F.; Vallés-García, C.; Montero-Lanzuela, E.; López-Francés, A.; Ferrer Ribera, RB.; Baldovi, HG.; Navalón Oltra, S. (2021). Hybrid sp2/sp3 nanodiamonds as heterogeneous metal-free ozonation catalysts in water. Applied Catalysis B Environmental. 299:1-11. https://doi.org/10.1016/j.apcatb.2021.12067311129

Mixed-metal Zr/Ti MIL-173 porphyrinic metal–organic frameworks as efficient photocatalysts towards solar-driven overall water splitting

International audienceA hydrolytically stable metal–organic framework containing Ti( iv ) and porphyrinic linkers allows a photoinduced charge separation process for the photocatalytic overall water splitting reaction