Designing bifunctional acid–base mesoporous hybrid catalysts for cascade reactions

Gianotti, Enrica; Díaz, Urbano; Velty, Alexandra; Corma, Avelino

doi:10.1039/c3cy00269a

Cited by 70 publications

(63 citation statements)

References 71 publications

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“…The design of bifunctional catalysts most often relies on combining simple, inexpensive catalytic elements on chemically functionalizable materials to enable cooperative interactions [2,3]. Examples of cooperative acid-base catalysts include homogeneous organocatalysts [4][5][6][7][8], polymeric systems [9], carbon quantum dots [10], and silica-immobilized systems [11][12][13][14][15][16][17][18][19]. The facile ability to separate and recycle heterogeneous catalysts from reactive fluids makes them attractive targets for incorporating acid-base cooperativity in new materials.…”

Section: Introductionmentioning

confidence: 99%

Reaction-dependent heteroatom modification of acid–base catalytic cooperativity in aminosilica materials

Moschetta

Brunelli

Jones

2015

Applied Catalysis A: General

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a b s t r a c tThe effects of heteroatom substitution on the cooperative catalytic activity of a series of bifunctional acid-base aminosilica catalysts are probed in aldol and nitroaldol condensations. Three M 3+ (B, Al, and Ga) and three M 4+ (Ti, Zr, and Ce) heteroatoms are incorporated into different samples of SBA-15 silica and then grafted with aminosilanes to produce bifunctional acid-base catalysts. The catalytic activity of each material is measured in the aldol condensation of 4-nitrobenzaldehyde with acetone at 50 • C and the nitroaldol condensation of 4-nitrobenzaldehyde with nitromethane at 40 • C and compared to the catalytic activity of a heteroatom-free aminosilica catalyst. The heteroatom substitutions produce catalysts with larger amounts of strong Lewis acid sites compared to the heteroatom-free aminosilica catalyst. We rationalize these results in the context of the physical (e.g. surface area, pore diameter, particle size) and chemical properties (e.g. total number and strength of acid sites) of each material and the proposed catalytic mechanisms of the two reactions. The increase in the number of strong Lewis acid sites of each heteroatom material decreased its activity in the aldol condensation, though four heteroatom substitutions (B, Al, Ga, and Ti) increased the catalytic activity of the aminosilica catalyst in the nitroaldol condensation. The results suggest that inclusion of a small amount of Lewis acid sites in aminosilica materials can increase the cooperative catalytic activity of the materials in the nitroaldol condensation. The results also suggest that inclusion of Lewis acid sites in aminosilica materials decreases the cooperative catalytic activity of the materials in the aldol condensation.

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Section: Introductionmentioning

confidence: 99%

Reaction-dependent heteroatom modification of acid–base catalytic cooperativity in aminosilica materials

Moschetta

Brunelli

Jones

2015

Applied Catalysis A: General

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“…SSHCs can be composed of isolated individual atoms or complexes, which are spatially separated without interaction, so each active site will have an equivalent energetic interaction with incoming reagents. This results in the generation of highly active and selective active sites, which have proved effective for catalysing a wide range of chemical transformations that have benefited both industry and society [2][3][4][5][6][7]. Researchers have long explored the development of such isolated active sites through isomorphous substitution within aluminosilicates (zeolites) and aluminophosphates (AlPOs), since their conception in 1982 [8].…”

Section: Introduction and Design Strategymentioning

confidence: 99%

Influence of dopant substitution mechanism on catalytic properties within hierarchical architectures

et al. 2016

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A range of hierarchically porous (HP) AlPO-5 catalysts, with isomorphously substituted transition metal ions, have been synthesized using an organosilane as a soft template. By employing a range of structural and spectroscopic characterization protocols, the properties of the dopant-substituted species within the HP architectures have been carefully evaluated. The resulting nature of the active site is shown to have a direct impact on the ensuing catalytic properties in the liquid-phase Beckmann rearrangement of cyclic ketones.

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“…According to the proposed mechanism, it can be suggested that the enormous hydroxyl groups on the surface of PMO‐ICS ( 1 ) are responsible for the primary activation of both carbonyl group of aldehydes 2 and malononitrile ( 4 ) by hydrogen bonding to facilitate nucleophilic addition of corresponding imine‐ketene resonance form of malononitrile ( 4′ ) on the activated aldehydes ( I ) and formation of intermediate ( II ) ,. The hygroscopic property of the inorganic silica moiety can promote the next step and formation of cyanocinnamonitrile intermediate ( III ) ,,. The PMO‐ICS ( 1 ) is also able to increase the enol form ( 3′ or 7′ ) concentration of 1,3‐dicarbonyls and subsequent Michael addition to afford intermediate ( IV ).…”

Section: Resultsmentioning

confidence: 99%

Green and Facile Synthesis of 4H-Pyran Scaffold Catalyzed by Pure Nano-Ordered Periodic Mesoporous Organosilica with Isocyanurate Framework (PMO-ICS)

Yaghoubi

Dekamin

2017

ChemistrySelect

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Isocyanurate bridging (PMO‐ICS) microporous, without any post‐modification using Bronsted and Lewis acid or base centers, was used as a highly active and recyclable bifunctional nano‐ordered catalyst for three‐component synthesis of diverse 4H‐pyran derivatives from enolizable compounds, different aldehydes and malononitrile under mild reaction conditions in good to excellent yields and short reaction times. Furthermore, the PMO‐ICS catalyst was also recovered and reused at least five times without significant loss of its catalytic activity. Elimination of any toxic heavy metals or corrosive reagents for modification of the catalytic activity, low loading of the catalyst, high to excellent yields, easy separation and purification of the products, and reusability of the catalyst are among significant advantages of this green protocol.

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Designing bifunctional acid–base mesoporous hybrid catalysts for cascade reactions

Cited by 70 publications

References 71 publications

Reaction-dependent heteroatom modification of acid–base catalytic cooperativity in aminosilica materials

Reaction-dependent heteroatom modification of acid–base catalytic cooperativity in aminosilica materials

Influence of dopant substitution mechanism on catalytic properties within hierarchical architectures

Green and Facile Synthesis of 4H-Pyran Scaffold Catalyzed by Pure Nano-Ordered Periodic Mesoporous Organosilica with Isocyanurate Framework (PMO-ICS)

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