Microporous Silica Prepared by Organic Templating: Relationship between the Molecular Template and Pore Structure

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• 作者：Yunfeng Lu ; Guozhong Cao ; Rahul P. Kale ; S. Prabakar ; Gabriel P. Ló ; pez ; and C. Jeffrey Brinker
• 刊名：Chemistry of Materials
• 出版年：1999
• 出版时间：May 1999
• 年：1999
• 卷：11
• 期：5
• 页码：1223 - 1229
• 全文大小：117K
• 年卷期：v.11,no.5(May 1999)
• ISSN：1520-5002

文摘

Microporous silica materials with a controlled pore size and a narrow pore size distributionhave been prepared by sol-gel processing using an organic-templating approach. Microporousnetworks were formed by pyrolytic removal of organic ligands (methacryloxypropyl groups)from organic/inorganic hybrid materials synthesized by copolymerization of 3-methacryloxypropylsilane (MPS) and tetraethoxysilane (TEOS). Molecular simulations and experimental measurements were conducted to examine the relationship between the microstructural characteristics of the porous silica (e.g., pore size, total pore volume, and poreconnectivity) and the size and amount of organic template ligands added. Adsorptionmeasurements suggest that the final porosity of the microporous silica is due to both primarypores (those present in the hybrid material prior to pyrolysis) and secondary pores (thosecreated by pyrolytic removal of organic templates). Primary pores were inaccessible to N₂at 77 K but accessible to CO₂ at 195 K; secondary pores were accessible to both N₂ (at 77 K)and CO₂ (at 195 K) in adsorption measurements. Primary porosity decreases with the amountof organic ligands added because of the enhanced densification of MPS/TEOS hybrid materialsas the mole fraction of trifunctional MPS moieties increases. Pore volumes measured bynitrogen adsorption experiments at 77 K suggest that the secondary (template-derived)porosity exhibits a percolation behavior as the template concentration is increased. Gaspermeation experiments indicate that the secondary pores are approximately 5 Å in diameter,consistent with predictions based on molecular simulations.