Hybrid organic–inorganic catalytic porous materials synthesized at neutral pH in absence of structural directing agents

Abstract

Non-ordered porous hybrid materials with different distribution of pore sizes have been synthesized from organic-inorganic bridged silsesquioxane precursors using an NH 4 F catalyzed sol-gel route. This methodology has allowed to obtain high surface area porous materials in absence of structural directing agents or surfactant molecules. A variety of organic linkers, such as benzene, disulfide, diamine, ethane and ethylene groups, were incorporated within the framework, and the effective integration was confirmed by elemental and thermogravimetrical analyses, Raman and NMR spectroscopies. The pore dimensions of the hybrids could be modified, within the mesoporous range, with the NH 4 F synthesis and the characteristics of the organic linker. Basic catalytic active sites have been introduced in the organic linkers of the hybrid porous materials that are active and selective for Knoevenagel condensations, showing the possibility to heterogenize organic catalysts while preserving their activity and selectivity by means of these porous organic-inorganic hybrids.

Polymeres graphitisches Kohlenstoffnitrid als heterogener Organokatalysator: von der Photochemie über die Vielzweckkatalyse hin zur nachhaltigen Chemie

“…Die Bor-Regionen an der Oberfläche kçnnen als starke Lewis-Säuren wirken, was die basischen Stickstoffe in Richtung einer difunktionellen Katalyse ergänzt. [54] Weitere strukturelle Details des Einbaus von Bor in den C/N-Kçrper wurden mittels 11 B-Festkçrper-MAS-NMRund XPS-Experimenten bestimmt. Das 11 B-NMR-Spektrum ergibt zwei Peaks, entsprechend den zwei mçglichen Positionen in der Gerüststruktur, der Ecken-und der Kantenlage (Abbildung 8).…”

“…[7][8][9] Feste, heterogene Katalysatoren sind effektiv und einfach aus der Reaktionsumgebung wiederzugewinnen, was zu verbesserten Prozessschritten mit hçherer Prozessçkonomie und umweltfreundlicherer Produktion führt. [10,11] Klassische anorganische Materialien sind in der Natur ihrer aktiven Stellen limitiert, und damit auch ihr Anwendungsbereich. [12] Organische Polymerkatalysatoren oder Katalysatorträger sind flexibel und kçnnen chemisch einfach optimiert werden, leiden aber traditionell an starker Quellung und Stabilitätsproblemen.…”

One-pot synthesis of hybrid mesoporous xerogels starting with linear polymethylhydrosiloxane and bridged bis-(trimethoxysilyl)ethane

“…The hybrid framework was evaluated by Fourier transform infrared spectrophotometry (FT-IR), and the spectra were recorded with KBr pellets using a Vertex 70 spectrophotometer from Bruker (4 cm À1 resolution) in the 4000 to 400 cm À1 region. The chemical structure of the hybrid material was determined by solid state 13 C CP/ 29 Si NMR experiments. The measurements were carried out at B 0 = 9.4 T on a Bruker AVANCE III 400 WB spectrometer.…”

“…most widely used 1,2-bis(trimethoxysilyl)ethane (BTME), 1,2-bis(triethoxysilyl)ethane (BTEE), 1,4-bis(triethoxysilyl)benzene and 1,2-bis(triethoxysilyl)ethylene [29,30]. Alkoxy groups can be hydrolyzed to reactive Si-OH, which can subsequently condense with the formation of Si-O-Si bridges.…”

Hybrid organic–inorganic catalytic mesoporous materials with proton sponges as building blocks

“…13 In this work, organic-inorganic hybrid materials with a proton sponge as the organic builder have been synthesized following a fluoride-catalysed sol-gel process, at neutral pH and low temperatures, that avoids the use of SDAs. 13,14 The proton sponges are diamines with neighboring atoms at short distance and aromatic frames, such as naphthalene and phenanthrene. 15 These molecules exhibit high unusual basicity, being 1,8-bis(dimethylamino)naphthalene (DMAN, scheme 1) with pKa=12.1, the archetype of proton sponge.…”