Synthesis and Characterization of Microporous Fe−Si−O Materials with Tailored Iron Content from Silsesquioxane Precursors

Abstract

Calcination of mixtures of (c-C 5 H 9 ) 7 Si 7 O 9 (OH) 3 , 1, and (c-C 5 H 9 ) 7 Si 7 O 12 Fe(tmeda), 2 (tmeda ) N,N,N′,N′tetramethylethylenediamine), led to microporous amorphous Fe-Si-O materials with adjustable iron content in the range 1-11 wt %. A set of different complementary techniques including N 2 physisorption, XRD, XPS, DRUV-vis, RS, IR, HRTEM, and Mo ¨ssbauer spectroscopy was used to follow the variation of the textural properties, metal dispersion, and speciation with the iron content along the whole mixing series. The calcination of these mixtures produced Fe-Si-O materials having basically the same properties as those observed for the individually calcined iron silsesquioxane. The N 2 physisorption indicates high surface areas, rather large pore volumes, and a very narrow pore size distribution with an average pore size diameter around 6-7 Å. The TEM and the spectroscopic analysis of the Fe-Si-O materials indicate that the iron is present mainly as small iron oxide particles highly dispersed throughout silica and to a minor extent as clustered and isolated species. The particle size distribution was estimated to be about 2-8 nm for 11% Fe-Si-O and 2-4 nm for samples with lower iron content. These materials showed catalytic activity in NH 3 oxidation and N 2 O decomposition.

Preparation of Novel Materials for Catalysts Utilizing Metal-Containing Silsesquioxanes

“…Irrespective of the kinds of precursor molecules, the pore size of the oxides in these studies falls within the range found in the porous materials prepared by the thermal treatment of discrete silsesquioxane molecules, including metallic species or not [46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62], and silsesqioxane polymers [81,91]. The thermogravimetric analyses support the idea that complete loss of the counter cation occurs during the heat-up before the formation of micropores started by the combustion of the cyclopentyl groups.…”

“…the preparation of chromium-containing silica from (c-C 5 H 9 ) 7 Si 7 O 9 (OSiMe 3 )O 2 CrO 2 and their catalytic activities for the oxidation of ammonia [57]. Microporous amorphous Fe-Si-O materials with adjustable iron content have been prepared by the calcination of mixtures of an iron-containing silsesquioxane and a metal-free one, which show the activity for ammonia oxidation and N 2 O decomposition [60]. The calcination of a three-component mixture of iron and chromium-containing molecules and metal-free molecules yields bimetallic Fe-Cr-Si-O materials [61].…”

Synthesis and Characterisation of Metal Isobutylsilsesquioxanes and Their Role as Inorganic–Organic Nanoadditives for Enhancing Polymer Thermal Stability

“…[8][9][10][11][12] These metal-containing cage structures have proved to be promising both as homogeneous catalysts and as precursors for highly efficient metal-based heterogeneous catalysts. [13][14][15][16] Since a wide variety of organic groups can be bound to the silicon, the inorganic cage can also show a tunable chemical affinity towards several organic solvents and also for polymeric matrices. Thus, these inorganic-organic hybrid molecular materials may be made chemically compatible towards polymers and become suitable for preparing nanocomposites.…”

Ti-bridged silsesquioxanes as precursors of silica-supported titanium oxide catalysts for the epoxidation of cyclooctene

“…While the formation of micropores by the calcination of POSS molecules has been previously reported [32][33][34][35][36][37][38][39][40][41][42][43][44], an increase in the BET surface area by the calcination of silica-supported POSS was not recognized from the results shown in Table 4, probably because of a low loading level of POSS.…”

“…In addition to their activities as homogeneous catalysts, their application to heterogeneous catalysis using metal-containing POSS as precursors has been examined [10,13,15,[24][25][26][27][28][29][30][31]. The preparation of microporous silicas containing well-dispersed metal oxide species by the controlled calcination of metal-containing POSS has been reported [32][33][34][35][36][37][38][39][40][41][42].…”