Publications by authors named "Nilton Rosenbach"

7 Publications

  • Page 1 of 1

Atomistic Mechanisms of Thermal Transformation in a Zr-Metal Organic Framework, MIL-140C.

J Phys Chem Lett 2021 Jan 15;12(1):177-184. Epub 2020 Dec 15.

Department of Mechanical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.

To understand the mechanisms responsible for thermal decomposition of a Zr-MOF (MIL-140C), we perform atomistic-scale molecular dynamics (MD) simulations and discuss the simulation data in comparison with the TEM images obtained for the decomposed Zr-MOF. First, we introduce the ReaxFF parameters suitable for the Zr/C/H/O chemistry and then apply them to investigate the thermal stability and morphological changes in the MIL-140C during heating. Based on the performed simulations we propose an atomic mechanism for the collapse of the MIL-140C and the molecular pathways for carbon monoxide formation, the main product of the MIL-140C thermal degradation. We also determine that the oxidation state of the ZrO clusters, evolved due to the thermal degradation, approximates the tetragonal phase of ZrO. Both simulations and experiments show a distribution of very small ZrO clusters embedded in the disrupted organic sheet that could contribute to the unusual high catalytic activity of the decomposed MIL-140C.
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http://dx.doi.org/10.1021/acs.jpclett.0c02930DOI Listing
January 2021

Dynamic behaviour of carbocations on zeolites: mobility and rearrangement of the C4H7(+) system.

Chem Commun (Camb) 2013 May 11;49(40):4480-2. Epub 2013 Apr 11.

Universidade Federal do Rio de Janeiro, Instituto de Química, Av Athos da Silveira Ramos 149, CT Bloco A, 21941-909, Rio de Janeiro, Brazil.

The mobility and rearrangement of the C4H7(+) system over Chabazite were studied using ab initio molecular dynamics. The results indicated the high mobility of the cations, which can rearrange within picosecond time intervals. Experimental studies of nucleophilic substitution supported the theoretical findings.
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http://dx.doi.org/10.1039/c3cc40627jDOI Listing
May 2013

Unusual chain-length dependence of the diffusion of n-alkanes in the metal-organic framework MIL-47(V): The Blowgun effect.

Chemistry 2010 Sep;16(34):10337-41

Institut de Recherches sur la Catalyse et l'environnement de Lyon, Université de Lyon, CNRS, 2. Av. A. Einstein, 69626 Villeurbanne, France.

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http://dx.doi.org/10.1002/chem.201001521DOI Listing
September 2010

Prediction of the conditions for breathing of metal organic framework materials using a combination of X-ray powder diffraction, microcalorimetry, and molecular simulation.

J Am Chem Soc 2008 Sep 27;130(38):12808-14. Epub 2008 Aug 27.

Laboratoire Chimie Provence, Universités d'Aix-Marseille I, II et III - CNRS, UMR 6264, Centre de Saint Jérôme, 13397 Marseille, France.

The adsorption of C1 to C4 linear hydrocarbons in the flexible metal organic framework MIL-53(Cr) has been followed by adsorption manometry coupled with microcalorimetry and Synchrotron X-ray powder diffraction. This experimental investigation was completed by molecular modeling. In the case of methane, the solid remains rigid whatever the adsorbate amount. However for the C2-C4 series, an increasing flexibility of the structure is observed, which is ascribed first to a breathing of the material from a large pore to a narrow pore form followed by a further expansion at high pressure. The collected thermodynamic and structural information suggests that a minimum adsorption enthalpy of ca. 20 kJ mol (-1) in the initial large pore structure of MIL-53(Cr) is required to induce the structural transition "large to narrow pore". Further, the enthalpy of adsorption can be used to predict the pressure at which the structure reopens. Finally, the magnitude of the breathing can be related to the size of the probe molecule via the van der Waals volume. The above trends have been successfully verified in the case of water and carbon dioxide. This combined experimental and theoretical approach gives the first elements for the prediction of whether or not the MIL53 and similar flexible structures will respond to gas loading and what would be the pressure required and further the amplitude of the induced breathing.
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http://dx.doi.org/10.1021/ja803899qDOI Listing
September 2008

Quasi-elastic neutron scattering and molecular dynamics study of methane diffusion in metal organic frameworks MIL-47(V) and MIL-53(Cr).

Angew Chem Int Ed Engl 2008 ;47(35):6611-5

Institut Charles Gerhardt Montpellier, Université Montpellier 2, Place E. Bataillon, 34095 Montpellier cedex 05, France.

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http://dx.doi.org/10.1002/anie.200801748DOI Listing
September 2008

Rearrangement, nucleophilic substitution, and halogen switch reactions of alkyl halides over NaY Zeolite: formation of the bicyclobutonium cation inside the zeolite cavity.

J Am Chem Soc 2008 Feb 12;130(5):1592-600. Epub 2008 Jan 12.

Universidade Federal do Rio de Janeiro, Instituto de Química, Av Athos da Silveira Ramos 149, CT Bloco A, Cidade Universitária 21941-909, Rio de Janeiro, Brazil.

Rearrangement and nucleophilic substitution of cyclopropylcarbinyl bromide over NaY and NaY impregnated with NaCl was observed at room temperature. The first-order kinetics are consistent with ionization to the bicyclobutonium cation, followed by internal return of the bromide anion or nucleophilic attack by impregnated NaCl to form cyclopropylcarbinyl, cyclobutyl, and allylcarbinyl chlorides. The product distribution analysis revealed that neither a purely kinetic distribution, similar to what is found in solution, nor the thermodynamic ratio, which favors the allylcarbinyl halide, was observed. Calculations showed that bicyclobutonium and cyclopropylcarbinyl carbocations are minimal over the zeolite structure, and stabilized by hydrogen bonding with the framework structure. A new process of nucleophilic substitution is reported, namely halogen switch, involving alkyl chlorides and bromides of different structures. The reaction occurs inside the zeolite pores, due to the confinement effects and is an additional proof of carbocation formation on zeolites. The results support the idea that zeolites act as solid solvents, permitting ionization and solvation of ionic species.
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http://dx.doi.org/10.1021/ja0742939DOI Listing
February 2008

A DFT study of the acidity of ultrastable Y zeolite: where is the Brønsted/Lewis acid synergism?

Angew Chem Int Ed Engl 2004 Jun;43(23):3050-3

Instituto de Química, Universidade Federal do Rio de Janeiro, Cidade Universitária CT, Bloco A, 21949-900 Rio de Janeiro, Brazil.

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http://dx.doi.org/10.1002/anie.200353049DOI Listing
June 2004