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Synthesis and Characterization of Novel Mesoporous Materials

Author: HuZuoFan
Tutor: WangYunHua；YuChengZhong
School: Fudan University
Course: Inorganic Chemistry
Keywords: mesoporous materials chirality organic/inorganic hybrid materials surfactant-free synthesis
CLC: TB383.4
Type: Master's thesis
Year: 2011
Downloads: 242
Quote: 1
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Abstract

Mesoporous materials have become a hot multidisciplinary research field at the interface of chemistry and materials science. In the last twenty years, mesoporous materials with various compositions, morphologies, pore structures, pore sizes and functions have been successfully synthesized, and their practical applications have been carefully investigated. Besides all these cheerful results and achievements, there are still big challenges in the in-depth understanding of their controlled synthesis, and further investigation of novel functional mesoporous materials and their application researches.Mesoporous silica, especially periodical mesoporous silica (PMS), is the most well-known material among all mesoporous materials. Traditional PMS materials generally possess 2-or 3-dimensional pore structures. Recently, helical mesoporous materials with chiral channels have attracted great interests due to their potential applications in asymmetric synthesis, separation and catalysis. Because the plain physical and chemical properties of amorphous silica itself limit its further application, a solution is to perform surface functionalization or use substitution of functional composition for silica. Meanwhile, the experience accumulated in the synthesis of mesoporous silica is beneficial to guide the preparation of mesoporous materials with other compositions. In this thesis, we have prepared a series of novel materials including chiral mesoporous silica with helical channels, organic/inorganic hybrid large-pore mesoporous materials, mesoporous calcium silicate hydrate materials under surfactant-free condition.In chapter 2, we synthesized enantiomorphic excessive helical mesoporous silica rods with chiral channels, using achiral surfactant cetyltrimethylammonium bromide (CTAB) as template, mandelic acid as chiral dopants, tetraethylorthosilicate (TEOS) as the silica source. An interesting relationship have been found between the diameter (D) and pitch (P) of silica rods by randomly choosing several rods and measuring their diameter and pitch from TEM images. It turns out that P showed a linear relationship as a function of D 5, as well as the P/D1.5 function is a straight line passing through the origin. What’s more, this method have been generalized to other chiral dopants such as tartaric acid.In chapter 3, periodic mesoporous organosilica (PMO) materials with ultra large mesopores and face centered cubic mesostructures were prepared using ethylene bridged organosilica as precursors and organic swelling agents as expander. It was found that lowering the synthesis temperature and acidity could both increase the pore size and enhance the regularity of our PMO materials. So the PMO materials were synthesized using a combinational strategy by both decreasing the temperature and acidity. When the synthesis temperature is 0℃and the acidity is 0.1 M HCl, the pore diameter of the PMO material reaches 33.6 nm, which is the largest among cubic PMO materials to our knowledge.In chapter 4, calcium silicate hydrate (CSH) materials with large pore volume and high surface area were synthesized using a surfactant-free route, which avoids a step to remove surfactants to generate mesopores or the influence of residue surfactants to materials in their biomedical applications. During the synthesis process, CSH gel is obtained under room temperature in water, and then an organic solvent exchange treatment is performed to maintain the porous structure of CSH gel. It is also demonstrated that CSH materials are good candidates for drug loading. Because of the bonding between calcium ion in the CSH materials and the carboxyl groups in ibuprofen, CSH materials have a high load capacity for drug molecules with carboxyl groups, thus show superior property compared to traditional silica materials. In addition, using simple hydrothennal method with cheap raw materials calcium nitrate and sodium silicate, CSH materials with large pore volume and high surface area have been successfully synthesized. The synthesis conditions such as temperature and acidity were also studied.

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