COMMUNICATIONSshow that the d(100) value decreases from about 36 A for AS-C,,TA-H, (Fig. 2b) to about 25 A for the calcined material ( Fig. 2c). The "A1 NMR spectra of calcined samples indicate some of the tetrahedrally coordinated Al centers are converted to octahedrally coordinated ones. Partial dealumination is not unexpected for an aluminosilicate structure with such a high Al content, but it is also possible that these A1 centers are still relatively strongly bound to the framework and the walls have become thicker and the pores smaller. We are currently exploring the structural details of these calcined materials and the possibility of removing the templates by other, less destructive, procedures.In summary, this work, together with our previous results on the Si,, precursor demonstrates that it is possible to organize inorganic oligomers with surfactants step by step into mesostructural materials. Incorporation of metallic elements, and other modifications in structure and composition can be carried out more easily and more effectively at the oligomer stage than with gel precursors. It is also possible to achieve true materials design and structure-tailoring through such a synthetic pathway by using suitable structure building blocks (e.g., oligomers) and by effectively controlling the structure assembling processes (e.g., condensation).
Esper.ir.r2enlul ProceciureCrystalline TMA-AI,Si, was prepared according to the literature procedure by slowly evaporating a solution containing TMA silicate and TMA aluminate in a 1 : 1 Si,'AI ratio [9]. The TMA-silicate solution was prepared by dissolving Ludox silica into a TMAOH solution to obtain a final concentration of 1 M for both Si and TMA.The TMA aluminate solution used was freshly prepared by hydrolyzing aluminum isopropoxide in a TMAOH solution to a filial Al concentration of 0.3% and ii TMA:AI ratio of 1 9 1 . The precipitation of AI,Si, with surfactants was performed by mixing an AI,Si, solution (typically, TMA-AI,Si, crystals (10 g) dissolved in H20(100g)) and a solution of a surfactant (for example. 12.3% C,,TACI (200 mL)). The C,,AM solution was prepared by dissolving dodecylainine in an aqueous solution containing an equivalent amount of hydrochloric acid. The precipitate-mother liquor mixtures were aged overnight to equilibrate the condensation. and the precipitates were then isolated by filtration. wabhed with distilled water at room temperature and air-dried. The vapor phase treatments of the resulting Al,Si,-C,,TA (17 = 16. 12) precipitates were carried out by using the procedure giwn in reference [8] but water alone was used in the present work rather than the HCI solution used for the Si,-C,,TA systems. The AI,Si,-C,,AM precipitate was treated in refluxing isopropyl alcohol (1' = 90 C) for 24 hours to achieve further condensation.