Self-assembled porous materials from cyclic ureas

有机和高分子化学计划支持南卡罗来纳大学的Linda Shimizu教授的工作，她将开发具有合理可调腔的均匀微孔材料。它们将被用作诱导反应选择性、主客体化学和分离的受限环境。已经证明，双尿素大环可预见地自组装成含有中空管状通道的多孔晶体。该组装是由非共价相互作用指导的，主要是尿素-尿素氢键和芳基堆积作用。苯醚双尿素的初始结构证明了这种方法的有效性，因为它按照设计组装成晶体，其中包含的晶体进入充满醋酸客体的管状通道。客体可以从形成多孔主体的晶体中移除，该主体表现出与开放框架微孔材料一致的1型气体吸附等温线。最近有研究表明，结晶型苯醚双尿素与客体分子结合，并且这些客体可以被可逆地移除和反弹，就像沸石一样。事实上，结晶苯醚双尿素可以作为反应的容器，以高转化率促进2-环己酮的高立体选择性头尾[2+2]光二聚反应。重点将集中在从刚性间隔物和尿素合成双尿素大环，因为通过调节间隔物的大小和形状，自组装将显示更大范围的空腔大小和内部性质。然后，可以在内部添加官能团来调节反应环境，从而产生可调的空腔，旨在结合特定的客人并催化反应。此外，这些多孔材料还将作为选择性光化学反应的环境和乙醇脱水的催化剂进行研究。由有机和高分子化学计划资助的这项工作将导致新的分子构建块，这些构建块可预测地自组装成管状超分子组件和多孔固体，已被寻求用作传感器、定向反应的模板、分离和催化剂载体以及金属隔离剂。在这个项目中接受培训的研究生将获得广泛的多学科背景，这将使他们能够追求广泛的科学职业。该奖项将支持本科生和高中生的首次研究经历。该奖项还将支持化学推广计划的加强和继续，该计划促进K-12学生与教师和熟练的科学研究人员之间的互动。将纳入新的实验，以满足教师的要求并与科学标准有关。

The Organic and Macromolecular Chemistry Program supports the work of Professor Linda Shimizu of the University of South Carolina who will develop homogeneous microporous materials with rationally tunable cavities. These will be used as confined environments for inducing selectivity in reactions, for host/guest chemistry, and for separations. It has been demonstrated that bis-urea macrocycles predictably self-assemble into porous crystals, which contain hollow tubular channels. The assembly is directed by non-covalent interactions, primarily urea-urea hydrogen bonds, and aryl stacking interactions. The initial structure, phenylether bis-urea, proves that this approach is valid, as it assembles as designed into crystals containing into tubular channels filled with acetic acid guests. The guests can be removed from these crystals forming a porous host that display a type 1 gas adsorption isotherm consistent with an open framework microporous material. Recently it has been shown that crystalline phenylether bis-urea binds guest molecules and that these guests can be removed and rebound reversibly, much like zeolites. In fact, crystalline phenylether bis-urea can be used as a container for reactions, promoting highly stereoselective head-to-tail [2+2] photodimerizations of 2-cyclohexenone in high conversion. Focus will be on the synthesis of bis-urea macrocycles from rigid spacers and ureas that upon self-assembly will display a greater range of cavity sizes and interior properties by modulating the size and shape of the spacers. Functional groups can then be added on the interior to tune the reaction environment and will lead to 'tunable' cavities, designed to bind specific guests and catalyze reactions. Also, these porous materials will be investigated as environments for selective photochemical reactions and as catalysts for alcohol dehydration.The funding of this work by the Organic and Macromolecular Chemistry Program will result in new molecular building blocks that predictably self-assemble into tubular supramolecular assemblies and porous solids that have been sought for applications as sensors, templates for directed reactions, as separation and catalyst supports, and for metal sequestering agents. Graduate students trained in this program will receive a broad multidisciplinary background that will empower them to pursue a wide range of scientific careers. This award will support the first research experiences of undergraduates and high school students. This award will also support the enhancement and continuation of a chemistry outreach program that fosters interactions between K-12 students and teachers and skilled scientific researchers. New experiments to meet teacher requests and to relate to science standards will be incorporated.