Elucidation of the Interaction Mechanism between Organic Chiral Cages with Biomolecules through Nuclear Magnetic Resonance and Theoretical Studies

[EN] A multinuclear NMR has been carried out to elucidate the mechanism of action of CC3-R box-type chiral materials for the separation of enantiomers, supported by theoretical calculations. The potential of these materials to be used as chiral resolution agents through NMR is evidence in this study.Program Severo Ochoa SEV-2016-0683 is gratefully acknowledged. S.S-F. thanks MEC for his Severo Ochoa Grant SPV-2013-067884, P.O.-B. thanks MEC for his Ramon y Cajal contract RYC-2014-16620. M.B. and F.R. thank the financial support by the Spanish Government (MAT2017-82288-C2-1-P and MAT2015-71842-P). The authors thank the MULTY2-HYCAT (EU-Horizon 2020 funded project under grant agreement no. 720783). The Electron Microscopy Service of the UPV is acknowledged for their help in sample characterization.Saez-Ferre, S.; Boronat Zaragoza, M.; Cantin Sanz, A.; Rey Garcia, F.; Oña-Burgos, P. (2018). Elucidation of the Interaction Mechanism between Organic Chiral Cages with Biomolecules through Nuclear Magnetic Resonance and Theoretical Studies. The Journal of Physical Chemistry C. 122(29):16821-16829. https://doi.org/10.1021/acs.jpcc.8b05069S16821168291222

Dispositivo de rotación de tubos de resonancia magnética nuclear

Número de publicación: ES2522718 A1 (17.11.2014) También publicado como: ES2522718 B1 (12.11.2015) Número de Solicitud: Consulta de Expedientes OEPM (C.E.O.) P201400655 (24.07.2014)La invención un dispositivo especialmente diseñado para llevar a cabo la agitación de un tubo de resonancia magnética nuclear (RMN) que comprende: un soporte (2) al que está fijado un motor (3) eléctrico de eje horizontal; un adaptador (4) de tubos (100) de resonancia magnética nuclear fijado al eje del motor (3) eléctrico; un sensor Hall (5) dispuesto para detectar una posición inicial de dicho eje; un medio (6) de procesamiento conectado al motor (3) eléctrico y al sensor Hall (5); un módulo (7) de comunicaciones para llevar a cabo la programación del medio (6) de procesamiento; y una interfaz (8) de control y visualización conectada al medio (5) de procesamiento para operar el dispositivo (1) y visualizar datos acerca de su funcionamiento.Universidad de Almerí

Cobalt nanoclusters coated with N-doped carbon for chemoselective nitroarene hydrogenation and tandem reactions in water

[EN] The development of active and selective non-noble metal-based catalysts for the chemoselective reduction of nitro compounds in aquo media under mild conditions is an attractive research area. Herein, the synthesis of subnanometric and stable cobalt nanoclusters, covered by N-doped carbon layers as core shell (CoaNC-800), for the chemoselective reduction of nitroarenes is reported. The Co@NC-800 catalyst was prepared by the pyrolysis of the Co(tpy)(2) complex impregnated on Vulcan carbon. In fact, the use of a molecular complex based on six N-Co bonds drives the formation of a well-defined and distributed cobalt core-shell nanocluster covered by N-doped carbon layers. In order to elucidate its nature, it has been fully characterized by using several advanced techniques. in addition, this as-prepared catalyst showed high activity, chemoselectivity and stability toward the reduction of nitro compounds with H-2 and under mild reaction conditions; water was used as a green solvent, improving the previous results based on cobalt catalysts. Moreover, the Co@NC-800 catalyst is also active and selective for the one-pot synthesis of secondary aryl amines and isoindolinones through the reductive amination of nitroarenes. Finally, based on diffraction and spectroscopic studies, metallic cobalt nanoclusters with surface CoNx patches have been proposed as the active phase in the Co@NC-800 material.The authors acknowledge the financial support from the Spanish Government (RTI2018-096399-A-I00) and the Program Severo Ochoa SEV-2016-0683. S. G. T. is thankful to MINECO for her FPU Ph.D. contract FPU16/02117. P. O.-B. is thankful to MICCIN for his Ramon y Cajal contract RYC-2014-16620 and to UPV for the grant PAID-06-18/SP20180172 The High-Resolution STEM data were recorded at the DME-UCA node of the ELECMI ICTS Spanish National Infrastructure for Electron Microscopy of Materials. JJC acknowledges financial support from MINECO/FEDER (Project MAT2017-97579-R). C. W. L. acknowledges the Visiting Researcher Fellowship from PRH 50.1 - ANP/FINEP Human Resources Program (Brazil).Gutiérrez-Tarriño, S.; Rojas-Buzo, S.; Lopes, CW.; Agostini, G.; Calvino, JJ.; Corma Canós, A.; Oña-Burgos, P. (2021). Cobalt nanoclusters coated with N-doped carbon for chemoselective nitroarene hydrogenation and tandem reactions in water. Green Chemistry. 23(12):4490-4501. https://doi.org/10.1039/d1gc00706h44904501231

Cobalt metal-organic framework based on layered double nanosheets for enhanced electrocatalytic water oxidation in neutral media

A new cobalt metal-organic framework (2D-Co-MOF) based on well-defined layered double cores that are strongly connected by intermolecular bonds has been developed. Its 3D structure is held together by π-π stacking interactions between the labile pyridine ligands of the nanosheets. In aqueous solution, the axial pyridine ligands are exchanged by water molecules, producing a delamination of the material, where the individual double nanosheets preserve their structure. The original 3D layered structure can be restored by a solvothermal process with pyridine, so that the material shows a "memory effect" during the delamination-pillarization process. Electrochemical activation of a 2D-Co-MOF@Nafion-modified graphite electrode in aqueous solution improves the ionic migration and electron transfer across the film and promotes the formation of the electrocatalytically active cobalt species for the oxygen evolution reaction (OER). The so-activated 2D-Co-MOF@Nafion composite exhibits an outstanding electrocatalytic performance for the OER at neutral pH, with a TOF value (0.034 s-1 at an overpotential of 400 mV) and robustness superior to those reported for similar electrocatalysts under similar conditions. The particular topology of the delaminated nanosheets, with quite distant cobalt centers, precludes the direct coupling between the electrocatalytically active centers of the same sheet. On the other hand, the increase in ionic migration across the film during the electrochemical activation stage rules out the intersheet coupling between active cobalt centers, as this scenario would impair electrolyte permeation. Altogether, the most plausible mechanism for the O-O bond formation is the water nucleophilic attack to single Co(IV)-oxo or Co(III)-oxyl centers. Its high electrochemical efficiency suggests that the presence of nitrogen-containing aromatic equatorial ligands facilitates the water nucleophilic attack, as in the case of the highly efficient cobalt porphyrins

A tandem process for in situ H2O2 formation coupled with benzyl alcohol oxidation using Pd-Au bimetallic catalysts

[EN] Alcohol oxidation is one of the most important industrial organic reactions. Traditionally, the best-suited catalysts are Pd, Pt and Au supported nanoparticles. The research community has recently started developing strategies for synthesizing carbon-supported Pd/Au bimetallic nanoparticles (NPs), leading to higher activities and selectivities. However, the metallic active species in these catalysts are usually generated using sodium borohydride (NaBH4), which is not synthetically easy to reproduce. In fact, minor modifications in pH, concentration and/or other parameters have a prominent effect on the nature of the promoted material. In this work, a robust process involving dihydrogen flow (H2) at 200 °C as a reducing agent for synthesizing Pd/Au supported bimetallic materials was considered an alternative to the common pathway. The physicochemical properties of the materials derived from different reducing reagents and of varying composition ranges were studied using HR-TEM, XRD, CO chemisorption, and XPS. Their stability and activity were also tested for benzyl alcohol oxidation to benzaldehyde under mild reaction conditions (60 °C, water as the solvent, and PO2 = 1.5 bar). Notably, a catalyst from the hydrogen reduction process with a metal composition of 0.8%Pd¿0.2%Au/C consisting of bimetallic clusters (¿1.5 nm) proved to be the best material (C = 94%, S = 99%). Catalytic performances were strongly correlated with structural properties, such as nanoparticle size and distribution, which, in turn, were affected by the reduction step and the metal composition range. Finally, the influence of oxidants on benzyl alcohol oxidation has also been studied, along with the first approach for the tandem in situ formation of H2O2 coupled with alcohol oxidation.The authors are thankful for the financial support by the Spanish Government (RTI2018-096399-A-I00 and PGC2018-097277-B-I00 funded by MICINN/AEI/10.13039/501100011033) and Junta de Andalucia (P20 01027 and PYC 20 RE 060 UAL). The electron microscopy service of the UPV is acknowledged for their help in sample characterization.Martínez, JS.; Mazarío, J.; Gutiérrez-Tarriño, S.; Galdeano-Ruano, CP.; Gaona Miguélez, JA.; Domine, ME.; Oña-Burgos, P. (2022). A tandem process for in situ H2O2 formation coupled with benzyl alcohol oxidation using Pd-Au bimetallic catalysts. Dalton Transactions. 51(46):17567-17578. https://doi.org/10.1039/D2DT02831J1756717578514

Bimetallic Intersection in PdFe@FeOx-C Nanomaterial for Enhanced Water Splitting Electrocatalysis

Supported Fe-doped Pd-nanoparticles (NPs) are prepared via soft transfor-mation of a PdFe-metal oraganic framework (MOF). The thus synthesized bimetallic PdFe-NPs are supported on FeOx@C layers, which are essential for developing well-defined and distributed small NPs, 2.3 nm with 35% metal loading. They are used as bifunctional nanocatalysts for the electro-catalytic water splitting process. They display superior mass activity for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), both in alkaline and acid media, compared with those obtained for benchmarking platinum HER catalyst, and ruthenium, and iridium oxide OER catalysts. PdFe-NPs also exhibit outstanding stability against sintering that can be explained by the protecting role of graphitic carbon layers provided by the organic linker of the MOF. Additionally, the superior electrocatalytic performance of the bimetallic PdFe-NPs compared with those of monometallic Pd/C NPs and FeOx points to a synergetic effect induced by Fe-Pd interactions that facilitates the water splitting reaction. This is supported by additional characterization of the PdFe-NPs prior and post electrolysis by TEM, XRD, X-ray photoelectron spectroscopy, and Raman revealing that dispersed PdFe NPs on FeOx@C promote interactions between Pd and Fe, most likely to be Pd-O-Fe active centers

Understanding the potential-induced activation of a cobalt MOF electrocatalyst for the oxygen evolution reaction

Metal–organic frameworks (MOFs) are attractive porous materials for electrocatalytic applications associated with carbon-free energy storage and conversion. This type of material usually requires a post-treatment to be used as electrocatalyst. The present work comprehensively investigates the electrochemical activation of a cobalt-MOF@Nafion composite that produces outstanding electrocatalytic performance for the water oxidation reaction at neutral pH. A detailed electrochemical characterization reveals that the electroactivation of the composite requires the participation of the oxygen evolution reaction (OER) and leads to a significant increase in the electroactive population of cobalt centers. It is shown that an increase of the applied activation potential in the OER region results in a faster electroactivation of the Co-MOF without affecting the intrinsic electrocatalytic properties of the active cobalt centers, as evidenced by the unique linear correlation between the electrocatalytic OER current and the population of electroactive cobalt. In addition, at structural level, it is shown that the electrochemical activation causes the partial disruption of the Nafion adlayer, as well as morphological changes of the Co–MOF particles from a compact, rounded morphology, before electrochemical activation, to a more open and expanded structure, after electroactivation; with the concomitant increase of the number of surface–exposed cobalt centers. Interestingly, these cobalt centers retain their coordinative chemistry and their laminar distribution in the nanosheets at the nanoscale, which is consistent with the preservation of their intrinsic electrocatalytic activity after potential–induced activation. In this scenario, these results suggest that only the electroactivated cobalt centers with good accessibility to the electrolyte are electrochemically active. This work provides a better understanding of the processes and structural changes underlying the electrochemical activation at neutral pH of a Co–MOF for boosting the electrocatalytic water oxidation reaction9 página

Cobalt Metal-Organic Framework based on two dinuclear secondary building units for electrocatalytic oxygen evolution

The synthesis of a new microporous metal-organic framework (MOF) based on two secondary building units, with dinuclear cobalt centers, has been developed. The employment of a well-defined cobalt cluster results in an unusual topology of the Co2-MOF, where one of the cobalt centers has three open coordination positions, which has no precedent in MOF materials based on cobalt. Adsorption isotherms have revealed that Co2-MOF is in the range of best CO2 adsorbents among the carbon materials, with very high CO2/CH4 selectivity. On the other hand, dispersion of Co2-MOF in an alcoholic solution of Nafion gives rise to a composite (Co2-MOF@Nafion) with great resistance to hydrolysis in aqueous media and good adherence to graphite electrodes. In fact, it exhibits high electrocatalytic activity and robustness for the oxygen evolution reaction (OER), with a turnover frequency number value superior to those reported for similar electrocatalysts. Overall, this work has provided the basis for the rational design of new cobalt OER catalysts and related materials employing well-defined metal clusters as directing agents of the MOF structure

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