A new solid acid catalyst: the first phosphonate and phosphonic acid functionalised microporous polysilsesquioxanes

Bridged polysilsesquioxane xerogels containing amine ( NH 2 ; NH(CH 2 ) 2 NH 2 ; NH) and thiol ( SH) groups were synthesized by hydrolytic polycondensation of 1,2-bis(triethoxysilyl)ethane, 1,4-bis(triethoxysilyl)benzene and appropriate trifunctionalized silanes in the presence of a fluoride-ion catalyst in an ethanol solution. 29 Si CP/MAS NMR give indication of the molecular framework of these materials formed by structural T 1 , T 2 and T 3 units. 3-aminopropyl or 3-mercaptopropyl groups accessible to proton or metal ions are fixed to the xerogel surface by the siloxane bonds. IR and 13 C CP/MAS NMR data clearly show that 3-aminopropyl groups form hydrogen bonds. The same data testify that all xerogels contain non-condensed silanol groups and some fraction of non-hydrolyzed ethoxygroups.Functionalized polysilsesquioxane xerogels obtained by means of organic spacers have a porous structure (500-1000 m 2 /g) and a high content of functional groups (1.0-2.7 mmol/g). AFM data indicate that xerogels are formed by aggregating primary particles-the size of such aggregates is in the range 30-65 nm. It was established that the main factors influencing the structure and adsorption properties considered hybrid materials are: the nature and geometrical size of the functional groups, spacer flexibility and, in some cases, the ratio of the reacting alkoxysilanes and the ageing time of the gel.

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“…) characteristics. This conclusion is confirmed by the results that were recently published (Aliev et al, 2000;Jurado-Gonzalez et al, 2001).…”

Section: Resultssupporting

confidence: 93%

Bridged Polysilsesquioxane Xerogels Functionalizated by Amine- and Thiol- Groups: Synthesis, Structure, Adsorption Properties

et al. 2005

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“…These efforts have broadened in scope to include control of the optical,1e thermomechanical, − and chemical properties. ,,,− Other research programs independently developed related sol−gel processing conditions for bridged polysilsesquioxanes using trimethoxysilyl groups instead of triethoxysilyl groups along with a number of new bridging groups. ,,,,− The bridging organic group has also been reported as an expedient means for securely attaching organic functionalities, such as dyes − or metals, ,,− to existing porous materials.…”

Section: Historical Backgroundmentioning

confidence: 99%

“…Representative monomers are shown in Figure . The organic fragments in the building blocks range from rigid arylenic ( 1 − 10 ), ,− acetylenic ( 11 − 13 ), ,, and olefinic ( 14 − 16 ) 14,15 bridging groups to flexible alkylenes ranging from 1 to 14 methylene groups ( 17 − 28 ) in length. ,− They also include a variety of functionalized groups such as amines ( 29 ), ethers ( 30 ), sulfides ( 31 − 33 ), phosphines, amides, ureas ( 34 ), carbamates, and carbonates ( 35 ). 21c, In addition, bridging groups have included organometallics in which the metal is part of the bridge ( 36 ) 28 or pendant to the bridge ( 37 ) …”

Section: Introductionmentioning

confidence: 99%

Bridged Polysilsesquioxanes. Molecular-Engineered Hybrid Organic−Inorganic Materials

2001

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The class of hybrid organic−inorganic materials called bridged polysilsesquioxanes are used for everything from surface modifiers and coatings to catalysts and membrane materials. This paper examines how bridged polysilsesquioxanes are prepared, processed, characterized, and used. In particular, it describes how attaching several “inorganic” cross-linking trialkoxysilanes on organic bridging groups permits facile formation of network polymers and gels with high levels of chemical functionality. There are a number of synthetic entries into bridged polysilsesquioxane monomers that have allowed a multitude of different bridging groups to be integrated into xerogels (dry gels) or aerogels (supercritically dried “air gels”). Much of the research to date has been successfully focused on engineering of the size of pores through the choice of the bridging groups. For example, materials with some of the highest known surface areas in porous materials have been prepared, and parameters allowing control of the pore size distributions are well understood. More recently, however, the focus has shifted to building functionality into the bridging groups to make materials with controlled porosity that are capable of selective adsorption or catalysis or electronic and optic effects. This is the area where the full potential of bridged polysilsesquioxanes as molecular-engineered materials is being explored.

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“…A typical example is the preparation of uniformly modified polysilsesquioxanes from 1,4-bis(triethoxysilyl)but-2-ene and HPO(OEt) 2 to get 1,4-bis(triethoxysilyl)-2-(diethylphosphonato)butane via a radical addition reaction, which was then transferred to an insoluble product by an acid-catalyzed sol-gel process (Scheme 1). 68 The corresponding phosphonic acid modified polysilsesquioxane 1 was isolated after treatment of the phosphonate with concentrated hydrochloric acid and characterized by multinuclear solid-state nuclear magnetic resonance (NMR) spectroscopy.…”

Section: A Solid Acidsmentioning

confidence: 99%

Applications of Sol−Gel-Processed Interphase Catalysts

2002

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A new solid acid catalyst: the first phosphonate and phosphonic acid functionalised microporous polysilsesquioxanes

Cited by 19 publications

References 13 publications

Bridged Polysilsesquioxane Xerogels Functionalizated by Amine- and Thiol- Groups: Synthesis, Structure, Adsorption Properties

Bridged Polysilsesquioxane Xerogels Functionalizated by Amine- and Thiol- Groups: Synthesis, Structure, Adsorption Properties

Bridged Polysilsesquioxanes. Molecular-Engineered Hybrid Organic−Inorganic Materials

Applications of Sol−Gel-Processed Interphase Catalysts

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