Center for Molecular Modeling - D. Esquivel

Facile synthesis of cooperative acid-base catalysts by clicking cysteine and cysteamine on an ethylene-bridged periodic mesoporous organosilica

kevin — Thu, 15 Oct 2015 15:13:43 +0000

J. Ouwehand, J. Lauwaert, D. Esquivel, K. Hendrickx, V. Van Speybroeck, J.W. Thybaut, P. Van der Voort

European Journal of Inorganic Chemistry

2016, 13-14, 2144-2151

2016

Abstract

A Periodic Mesoporous Organosilica (PMO) containing ethylene bridges was functionalized in order to obtain a series of cooperative acid-base catalysts. A straightforward, single-step procedure was devised to immobilize cysteine and cysteamine on the support material via a photoinitiated thiol-ene click reaction. Likewise, PMO materials capped with hexamethyldisilazane (HMDS) were used to support both compounds. This resulted in different materials, where the amine site was promoted by carboxylic acid groups, surface silanol groups or both. The catalysts were tested in the aldol reaction of 4-nitrobenzaldehyde and acetone. It was found that silanol groups have a stronger promoting effect on the amine than the carboxylic acid group. The highest turnover frequency (TOF) was obtained for an amine functionalized material which only contained silanol promoting sites. The loading of the active sites also has a significant effect on the activity of the catalysts, which was rationalized based on a computational study.

DOI

http://dx.doi.org/10.1002/ejic.201501179

Private attachment

16-Eur-J-Inorg-Chem-xx(x)-Ouwehand.pdf

Au@UiO-66: a base free oxidation catalyst

michel — Wed, 12 Nov 2014 16:36:37 +0000

K. Leus, P. Concepcion, M. Vandichel, M. Meledina, A. Grirrane, D. Esquivel, S. Turner, D. Poelman, M. Waroquier, V. Van Speybroeck, G. Van Tendeloo, H. Garcia, P. Van der Voort

RSC Advances

5 (29), 22334–22342

2015

Abstract

We present the in situ synthesis of Au nanoparticles within the Zr based Metal Organic Framework, UiO-66. The resulting Au@UiO-66 materials were characterized by means of N2 sorption, XRPD, UV-Vis, XRF, XPS and TEM analysis. The Au nanoparticles (NP) are homogeneously distributed along the UiO-66 host matrix when using NaBH4 or H2 as reducing agents. The Au@UiO-66 materials were evaluated as catalysts in the oxidation of benzyl alcohol and benzyl amine employing O2 as oxidant. The Au@MOF materials exhibit a very high selectivity towards the ketone (up to 100 %). Regenerability and stability tests demonstrate that the Au@UiO-66 catalyst can be recycled with a negligible loss of Au species and no loss of crystallinity. In situ IR measurements of UiO-66 and Au@UiO-66-NaBH4, before and after treatment with alcohol, showed an increase in IR bands that can be assigned to a combination of physisorbed and chemisorbed alcohol species. This was confirmed by velocity power spectra obtained from the molecular dynamics simulations. Active peroxo and oxo species on Au could be visualized with Raman analysis.

Open Access version available at UGent repository

DOI

http://dx.doi.org/10.1039/C4RA16800C

Private attachment

15_RSC_Adv_5_22334_Leus.pdf

Au@UiO-66 : a base free oxidation catalyst

samuel — Thu, 06 Feb 2020 09:59:43 +0000

K. Leus, P. Concepcion, M. Meledina, M. Vandichel, A. Girrane, D. Esquivel, S. Turner, D. Poelman, M. Waroquier, V. Van Speybroeck

ISBN/ISSN:

Talk

Conference / event / venue

16th Netherlands' Catalysis and Chemistry Conference (NCCC-XVI)

Noordwijkerhout, The Netherlands

Monday, 2 March, 2015 to Wednesday, 4 March, 2015

Au@UiO-66: a base free oxidation catalyst (vol 5, pg 22334, 2015)

wim — Tue, 28 Apr 2015 07:41:40 +0000

K. Leus, P. Concepcion, M. Meledina, A. Grirrane, D. Esquivel, S. Turner, D. Poelman, M. Waroquier, V. Van Speybroeck, G. Van Tendeloo, H. Garcia, P. Van der Voort

RSC Adv.

2015

Correction