Pore size engineering in mesoporous silicas using supercritical CO2.

John P Hanrahan; Mark P Copley; Kirk J Ziegler; Trevor R Spalding; Michael A Morris; David C Steytler; Richard K Heenan; Ralf Schweins; Justin D Holmes

doi:10.1021/la0470636

PubMed · 15835989

Pore size engineering in mesoporous silicas using supercritical CO2.

John P Hanrahan·Mark P Copley·Kirk J Ziegler·Trevor R Spalding·Michael A Morris·David C Steytler·Richard K Heenan·Ralf Schweins·Justin D Holmes

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Abstract

In this paper we investigate the use of supercritical carbon dioxide (sc-CO(2)) for synthesizing calcined mesoporous silicas with tunable pore sizes, wall thickness, and d spacings. Small angle neutron scattering was used to probe the controlled swelling of the triblock copolymer surfactant templating agents, P123 (PEO(20)PPO(69)PEO(20)), P85 (PEO(26)PPO(39)PEO(26)), and F127 (PEO(106)PPO(70)PEO(106)), as a function of CO(2) pressure. The transition from the liquid crystal phase to the calcined mesoporous silicas, formed upon condensation and drying, was also studied in detail. Powder X-ray diffraction, transmission electron microscopy, and nitrogen adsorption techniques were used to establish pore diameters, silica wall widths, and the hexagonal packing of the pores within the calcined silicas. Using a direct templating method, the diameters of mesopores and the spacing between the pores could be tuned with a high level of precision. The swelling process was observed to have no detrimental effects on the quality of silica formed, a distinct advantage over conventional swelling techniques, and all of the silicas synthesized in this study were highly ordered over distances of at least 2000 A.

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Adsorption Aluminum Hydroxide Carbon Dioxide Magnesium Hydroxide Microscopy, Electron, Transmission Nitrogen Phase Transition Porosity Silicon Dioxide Surface Properties Surface-Active Agents X-Ray Diffraction Journal Article Research Support, Non-U.S. Gov't

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John P Hanrahan, Mark P Copley, Kirk J Ziegler, Trevor R Spalding, Michael A Morris, David C Steytler, Richard K Heenan, Ralf Schweins, Justin D Holmes. 2005-04-26. Pore size engineering in mesoporous silicas using supercritical CO2.. https://doi.org/10.1021/la0470636

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