Efficient Bifunctional Nanocatalysts by Simple Postgrafting of Spatially Isolated Catalytic Groups on Mesoporous Materials

Abstract

Hard graft pays off for Henry: An efficient acid–base bifunctional mesoporous catalyst was prepared by one‐step post‐synthesis grafting of aminoorganoalkoxysilane groups on mesoporous silica (see picture). The catalyst led to yields of over 99 % in the Henry reaction (nitroaldol condensation) of p‐hydroxybenzaldehyde and nitromethane to form nitrostyrene.

Silylation of montmorillonite surfaces: Dependence on solvent nature

“…That is to say, the silylated Mts prepared in the polar-protic solvents kept the swelling property as pristine Mt. On the contrary, the absence of hydrogen bond between silane molecules and nonpolar solvent molecules leads to a higher degree of condensation among silane molecules and between silane molecules and Mt surfaces [21,33]. In this case, a bridge of polysiloxane oligomers was formed between the adjacent layers as depicted in Fig.…”

Silicon‐Assisted Direct Covalent Grafting on Metal Oxide Surfaces: Synthesis and Characterization of Carboxylate N,N′‐Ligands on TiO2

“…[9] The nature of the resulting material depends heavily on the experimental conditions used during the grafting and parameters such as the temperature, the dilution, or the polarity of the solvent often lead to products having different properties. [10,11] Equally important are titania matrices onto which organic moieties bearing generally carboxylic acid functions have been grafted, almost exclusively by adsorption phenomena, and thoroughly studied by various spectroscopic techniques. [12][13][14][15][16][17] Among these, many have also been combined with, in particular, ruthenium chromophores and used as efficient photosensitizers.…”

Synthesis, Characterization, and Catalytic Properties of Two Zwitterionic Hybrid SBA‐15 Mesoporous Silicas

“…20 H, M av = 5800} and N- [3-(triethoxysilyl)propyl]-4,5-dihydroimidazole (TPDIm) were purchased from Aldrich Co. and used in the reactions without further purification. All solvents, such as THF and ethyl acetate, were analytical reagent grade and used as received.…”

“…[10][11][12] Recently, base-and acid-bifunctional mesoporous catalysts were developed and received great attention because a cooperative catalytic system constructed from general acid and base groups is desired for some carbon-carbon bondformation reactions. [13][14][15] Lin et al demonstrated that a general acid group, the ureidopropyl group, can activate substrates in cooperation with a general base group, the 3-[2- [a] [19][20] Kan et al synthesized acid-base bifunctional mesoporous materials by controlling steric hindrance to prevent interactions between acid and base. [13] Although much effort has been made, precise control of the molar ratio and distribution of the acid and base centers to avoid their neutralization is still a big challenge.…”

“…[17][18] Asefa et al prepared an efficient mesoporous catalyst containing spatially distributed organoamine and silanol groups by one-pot postgrafting. [19][20] Kan et al synthesized acid-base bifunctional mesoporous materials by controlling steric hindrance to prevent interactions between acid and base. [13] Although much effort has been made, precise control of the molar ratio and distribution of the acid and base centers to avoid their neutralization is still a big challenge.…”