Optimized Synthetic Strategies, Structures, Properties and Modification of Open Framework Oxides with High Ion Exchange Capacity

该项目主要研究微孔和沸石材料，这些材料具有带负电荷的框架，有规则间隔的孔和分子尺度的通道，具有阳离子交换特性，有时可以根据大小和形状区分离子和/或气体。除了为发现具有这些特性的新材料制定策略外，了解任何选择性的结构基础也很重要。最近使用同步辐射获得的结构结果，提出了增加离子交换能力的策略。假设低价金属可以取代框架结构中常见的高价金属，例如锂代替硅，从而产生具有增强离子交换能力和选择性的高负电荷框架。锂的晶体化学性质使其在这方面成为理想的选择，并且对几种新岩石硅酸盐的研究表明其具有丰富的结构化学。将进行合成以扩大在框架中含有Li的材料范围，包括尝试调整“纯”二氧化硅和铝硅酸盐分子筛的交换特性。这将与研究这些新材料的吸附和催化性能之间的关系相结合。锂取代成四面体网络的延伸是钠取代成八面体网络。这有效地降低了框架上的阳离子电荷，增加了框架外阳离子的数量，从而增加了离子交换能力。这种合成原理的第一个例子的结构是基于化学性质Na4[Na8Nb12.8Ti3.2]O44.8(OH)3.2 h2o的八面体分子筛（OMS）。我们正计划扩大这类材料的目录，并寻找它们对锶选择性的结构基础。这些类别的材料在分离、污染物去除和隔离应用中具有潜在的用途。它们对环境技术很重要，这些技术通过强调避免污染和优化避免和预防污染的测量、评估和反馈的新方法来改善补救和缓解，并降低未来的清理成本。它还将通过提供可用于改善制造过程及其环境影响的材料来影响工业生态。在这些高科技领域受过训练的学生很可能在未来的就业市场上具有很强的竞争力。

This project focuses on microporous and zeolitic materials with negatively charged frameworks, regularly spaced pores and channels of molecular dimension that possess cation-exchange properties that can sometimes discriminate between ions and/or gases based upon size and shape. Apart from formulating strategies for the discovery of new materials with these characteristics, it is important to understand the structural basis for any selectivity. Recent structural results, obtained using synchrotron radiation, suggest strategies to increase ion exchange capacity. It is hypothesized that low valent metals can replace common higher valent ones in framework structures, lithium for silicon for example, thereby producing highly negatively charged frameworks with enhanced ion exchange capacity and selectivity. The crystal chemistry of lithium makes it ideal in this regard and investigations of several new lithosilicates indicate a rich structural chemistry. Syntheses to expand the range of materials with Li in the framework will be pursued, including attempts to tailor the exchange properties of "pure" silica and aluminosilicate molecular sieves. This will be coupled with studies of the relationships between the sorbtive and catalytic properties of these new materials. An extension of Li-substitution into tetrahedral networks is the substitution of Na into octahedral networks. This effectively lowers the cationic charge on the framework and increases the number of extraframework cations and so ion exchange capacity. The structure of the first example of this synthetic philosophy is an Octahedral Molecular Sieves (OMS) based on the chemistry Na4[Na8Nb12.8Ti3.2]O44.8(OH)3.2o8H2O. We are planning to expand the catalogue of such materials and to seek the structural basis for their selectivity toward strontium. These classes of materials are potentially useful in separation, contaminant removal and sequestration applications. They are important to environmental technologies that improve remediation and mitigation, and decrease future cleanup costs by emphasizing pollution avoidance and novel approaches to the measurement, assessment, and feedback for the optimization of pollution avoidance and prevention. It will also impact industrial ecology by providing materials that can be applied to improve manufacturing processes and their environmental impact. Students trained in these areas of high-technology will likely be very competitive in the future job market.