Non-hydrolytic sol-gel reactions based on condensation of two functional groups are studied as an alternative to aqueous techniques for the synthesis of multimetallic oxides and inorganic-organic hybrid materials in the form of xerogels, nanoparticles, and thin films. We developed a non-hydrolytic sol-gel route based on acetic acid ester elimination providing parent phosphosilicate and its hybrid inorganic-organic derivatives. The polycondensation reactions between Si(OAc)4 and OP(OSiMe3)3 provides microporous phosphosilicate xerogels with surface areas up to 570 m2 g-1. Substitution reactions of residual acetoxy and trimethylsiloxy groups on the surface with a variety of reagents, such as SiCl4, RSiCl3, POCl3, AlX3, ROH, and Me3SiOSiMe3, show versatility of the synthesized phosphosilicate xerogels in tuning their properties, such as Br�nsted and Lewis acidity. The consecutive substitution of Si and P precursors by acetoxysilanes 1RxSi(OC(O)CH3)4-x (1R = Me, Ph; x = 1-2) and trimethylsilylesters of phosphonic acid 2RP(O)(OSiMe3)2 (2R = c-Hex, Ph) caused the decrease of surface areas and increase of average pore sizes because of the lower cross-linking ability of the substituted precursors. To avoid a significant decrease of surface areas of hybrid xerogels we used as precursors acetoxysilanes and phosphonic acid esters with bridging alkyl or aryl groups, such as (AcO)3Si-(CH2)x-Si(OAc)3 (x = 1-3, 6) and (Me3SiO)2P(O)-3R-P(O)(OSiMe3)2 (3R = C2H4, C6H4). We were able to tune the pore size of resulting xerogels to the mesoporous range. The prepared xerogels were characterized by elemental analyses, solid-state 13C, 29Si, 31P NMR spectroscopy, IR spectroscopy, surface area analysis, thermal analysis TG/DSC, and XRD measurements. The financial support by LH11028 is gratefully acknowledged.

Mesoporous hybrid inorganic-organic phosphosilicates by non-hydrolytic sol-gel reactions

248th National Meeting (2014)

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