Cooperative Catalysis by General Acid and Base Bifunctionalized Mesoporous Silica Nanospheres

Huh, Seong; Chen, Hung‐Ting; Wiench, Jerzy W.; Pruski, Marek; Lin, Victor S.-Y.

doi:10.1002/anie.200462424

Cited by 349 publications

(195 citation statements)

References 18 publications

(14 reference statements)

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“…Indeed, the weakly acidic silanol groups on the surface of silica have been previously recognized as capable of assisting various reactions. [23,[45][46][47][48][49] To test the participation of silanol groups in the catalytic process, we treated MAP-MSN-3.5 with hexamethyldisilazane (HMDS). 29 Si NMR showed that this reduced the number of silanols by 39% (from 3.8 to 2.3 mmol/g, Figure 4).…”

Section: Cooperative Effects Of the Supportmentioning

confidence: 99%

Substrate inhibition in the heterogeneous catalyzed aldol condensation: A mechanistic study of supported organocatalysts

Kandel

Althaus

Peeraphatdit

et al. 2012

Journal of Catalysis

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137

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In this study, we demonstrate how materials science can be combined with the established methods of organic chemistry to find mechanistic bottlenecks and redesign heterogeneous catalysts for improved performance. By using solid-state NMR, infrared spectroscopy, surface and kinetic analysis, we prove the existence of a substrate inhibition in the aldol condensation catalyzed by heterogeneous amines. We show that modifying the structure of the supported amines according to the proposed mechanism dramatically enhances the activity of the heterogeneous catalyst. We also provide evidence that the reaction benefits significantly from the surface chemistry of the silica support, which plays the role of a co-catalyst, giving activities up to two orders of magnitude larger than those of homogeneous amines. This study confirms that the optimization of a heterogeneous catalyst depends as much on obtaining organic mechanistic information as it does on controlling the structure of the support. Disciplines Materials Chemistry | Other Chemistry | Physical ChemistryComments NOTICE: this is the author's version of a work that was accepted for publication in Journal of Catalysis. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Catalysis, [291, (2012) AbstractIn this study we demonstrate how materials science can be combined with the established methods of organic chemistry to find mechanistic bottlenecks and redesign heterogeneous catalysts for improved performance. By using solid-state NMR, infrared spectroscopy, surface and kinetic analysis, we prove the existence of a substrate inhibition in the aldol condensation catalyzed by heterogeneous amines. We show that modifying the structure of the supported amines according to the proposed mechanism dramatically enhances the activity of the heterogeneous catalyst. We also provide evidence that the reaction benefits significantly from the surface chemistry of the silica support, which plays the role of a co-catalyst, giving activities up to two orders of magnitude larger than those of homogeneous amines. This study confirms that the optimization of a heterogeneous catalyst depends as much on obtaining organic mechanistic information as it does on controlling the structure of the support.

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Section: Cooperative Effects Of the Supportmentioning

confidence: 99%

Substrate inhibition in the heterogeneous catalyzed aldol condensation: A mechanistic study of supported organocatalysts

Kandel

Althaus

Peeraphatdit

et al. 2012

Journal of Catalysis

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137

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“…A cooperative catalytic mechanism that 90 emulates enzymatic chemistry was proposed to explain this unique behavior (Figure 3). 114 A later study found a dependency of the catalytic activity of the bi-functional materials on the density of the immobilized groups. Besides creating cooperative interactions, the introduction of two functional groups in MSN can be exploited to attain another desirable characteristic in a catalyst: selectivity.…”

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confidence: 96%

Mesoporous silica nanoparticles: structural design and applications

et al. 2010

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The structural properties of mesoporous silica nanoparticles are reviewed. Different strategies for the introduction of functional groups are considered. Based on the architectural features of the material, the functionalization at defined regions of the particles is described, along with the properties emerging from the corresponding site-specific modifications of their chemistry. Many applications derived from the unique architecture and chemistry of these nanostructured composite materials are shown. Disciplines Materials Chemistry | Other Chemistry CommentsThis a manuscript of an article from the Journal of Materials Chemistry 20 (2010) The structural properties of mesoporous silica nanoparticles are reviewed. Different strategies for the introduction of functional groups are considered. Based on the architectural features of the material, the functionalization at defined regions of the particles is described, along with the properties emerging from the corresponding site-specific modifications of their chemistry. Many 10 applications derived from the unique architecture and chemistry of these nanostructured composite materials are shown.

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“…These heterogeneous bifunctional catalysts can be categorized into three types: (1) catalysts possessing both an immobilized Brønsted acid site and a basic site derived from organic groups, (2) immobilized basic organic groups and Brønsted acid sites derived from the support surface, and (3) immobilized metal complexes or metal nanoparticles and basic organic groups. For a type (1) catalyst, in 2005, Lin and co-workers demonstrated a urea _ amine bifunctionalized silica surface for carbon _ carbon bond-forming reactions, such as an aldol reaction 6) . The first report on the immobilization of two incompatible groups, such as an organic acid (carboxylic or sulfonic acid), and a base, on the same catalyst particle surface was reported by Davis and co-workers in 2006 7) .…”

Section: Introductionmentioning

confidence: 99%

Synergistic Catalysis by Multifunctionalized Solid Surfaces for Nucleophilic Addition Reactions

Motokura

2014

J. Jpn. Petrol. Inst.

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This review paper treats with acid-base and Pd-complex-base bifunctional catalyst surfaces used to catalyze nucleophilic addition reactions. A silica _ alumina-supported tertiary amine was found to be a highly active hetero geneous catalyst for Michael additions and cyano-ethoxycarbonylation. These reactions barely proceeded with either a homogeneous amine or silica _ alumina support, indicating that synergistic catalysis occurred between the silica _ alumina surface and basic amine. Silica _ alumina, which contains both tertiary and primary amines, was an efficient catalyst for one-pot synthesis of 1,3-dinitroalkanes from aldehydes and nitromethane. The acidbase synergistic catalysis was applied to metal complex-base synergistic catalysis. Both the Pd-complex and tertiary amine-immobilized silica was an excellent heterogeneous catalyst for the Tsuji-Trost reaction. Spectroscopic analyses, such as solid-state MAS NMR, revealed the structures of prepared catalysts, immobilization mechanism of amine groups on the silica _ alumina surface, and reaction intermediates and catalytic reaction mechanism. Substrate scope for the cyanation, Michael reaction, 1,3-dinitroalkane synthesis, and the Tsuji-Trost reaction are also described.

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Cooperative Catalysis by General Acid and Base Bifunctionalized Mesoporous Silica Nanospheres

Cited by 349 publications

References 18 publications

Substrate inhibition in the heterogeneous catalyzed aldol condensation: A mechanistic study of supported organocatalysts

Substrate inhibition in the heterogeneous catalyzed aldol condensation: A mechanistic study of supported organocatalysts

Mesoporous silica nanoparticles: structural design and applications

Synergistic Catalysis by Multifunctionalized Solid Surfaces for Nucleophilic Addition Reactions

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