| Popis |
We developed non-hydrolytic sol-gel routes to several families of metallosilicate and phosphosilicate hybrid inorganic-organic materials based on polycondensation reactions between acetoxysilanes 1RxSi(OC(O)CH3)4-x (1R = Me, Ph; n = 0-2), phosphoric and phosphonic acid trimethylsilylesters 2RP(O)(OSiMe3)2 (2R = OSiMe3, c-Hex, Ph), metal amides M(N3R2)n (M = Al, Ti; 3R = Me, Et; n = 3, 4) and metal alkoxides M(O4R)n (M = Al, Ti; 4R = i-Pr, t-Bu, SiMe3; n = 3, 4) in aprotic dry solvents. Alumosilicate xerogels were prepared by polycondensation reactions between Al(NMe2)3 or Al(Oi-Pr)3 and acetoxysilanes. These elimination reactions led to the formation of Si-O-Al networks and released dimethylacetamide or acetic acid ester and as byproducts, respectively. Titanosilicate xerogels were prepared by non-hydrolytic polycondensation reactions between Ti amides Ti(NR2)4 (R = Me, Et) or Ti alkoxides Ti(OR)4 (R = i-Pr, t-Bu, SiMe3) and acetoxysilanes. The acetamide and ester elimination reactions led to Si-O-Ti networks. Phosphosilicates were prepared by the elimination of acetic acid ester from acetoxysilanes and trimethylsilyl phosphates and phosphonates. Two-step sequential polycondensation procedure was used to prepare metallosilicophosphates. The inorganic-organic hybrid xerogels contained residual surface organic groups that were employed for the chemical modification reactions on the surface by a variety of reagents, such as alcohols, chlorosilanes, metal alkyls and chlorides. Our aim was to study the versatility of these reactions, attain stoichiometry control, and tune the properties of resulting xerogels, such as surface area and Bronsted/Lewis acidity. The prepared xerogels were characterized by solid-state 13C, 27Al, 29Si, 31P NMR, IR, surface area analysis, TGA, XANES/EXAFS, and XRD.
|
