Chiral molecular fluoridosilicates and their twin polymerization for the preparation of fluorine-doped mesoporous silica and microporous carbon12. Issue 10 (18th September 2018) - Roschke, Felix
Abstract : The synthesis of organic–inorganic hybrid materials, microporous carbon and fluorine-doped mesoporous silica by the twin polymerization of pentacoordinated fluoridosilicates is reported. Abstract : The syntheses of chiral pentacoordinated fluoridosilicates and their conversion into fluorine-doped silica and mesoporous carbon are reported. Starting from 4 H, 4′ H -2, 2′-spirobi[benzo[ d ][1, 3, 2]dioxasiline] (1 ) and 8, 8′-di- tert -butyl-4 H, 4′ H -2, 2′-spirobi[benzo[ d ][1, 3, 2]dioxasiline] (2 ), the corresponding fluorido complexes3 and4 were obtained by the addition of potassium fluoride to the spirocyclic silicon salicylic alcoholates1 and2 in the presence of 18-crown-6. The pentacoordinated geometry around the silicon atom of the SiO4 F type in3 and4 was proved using single-crystal X-ray diffraction analysis. DSC measurements were used to study the thermal behavior of the compounds with regard to their usability in the twin polymerization process. Hence, polymerization of3 and4 and the simultaneous twin polymerization of the fluoridosilicate3 with spirocyclic1 gave fluorine-doped phenolic resin/silica composites as confirmed by solid state NMR spectroscopic studies ( 1 H, 13 C{ 1 H}, 19 F, and 29 Si{ 1 H}). Carbonization of the as-obtained hybrid materials and subsequent treatment with hydrofluoric acid resulted in microporous carbon with surface areas up to 1060 m 2 g −1 . Calcination of the hybrid materials produced fluorine-doped silica with BET surface areas up to 239 m 2 g −1 . Additionally, the synthesis of hybrid materials using the additive assisted twin polymerization of1 with either tetra- n -butylammonium fluoride or KF gave either microporous carbon (1219 m 2 g −1 ) or mesoporous silica (687 m 2 g −1 ).