Confinement effects within metal organic nanotubes: Relationships between hydrophobicity and water structure, diffusion, and selectivity

第一部分： 限制在纳米尺寸通道中的水可以以意想不到的方式表现，并且控制这种行为可以导致用于水净化应用的新材料的开发。 排列在这些纳米通道内壁上的化学成分的身份可能是关键的设计原则，可以用来创造具有可控水特性的新材料。 该项目的总体假设是，组成通道壁的化学成分的身份和位置是控制这些空间内的水的关键。金属有机纳米管（蒙茨）被用来测试这一假设，因为它们包含一维通道，具有可调的通道壁，并表现出在水中的稳定性。 在该项目中，由材料研究部的固态和材料化学计划支持，蒙茨设计有化学成分，可以吸引或排斥内墙沿着特定位置的水分子。 然后，通过确定封闭水分子在通道内的组织方式，测量水通过通道的运动速率，并测试蒙茨选择性地吸收水而不是其他分子的能力，来探索这些新材料内封闭水的行为。 获得承压水的基本知识对于创造用于水净化和处理的先进材料非常重要。 该项目的其他教育举措包括复原力培训和克服失败，以提高学生对科学的保留。 这包括本科生和研究生课程的制定，将免费传播给该领域的其他人。这些努力还将包括评估和评价最佳实践，以进一步了解弹性培训在提高STEM保留率方面的作用。 第二部分： 预测和控制纳米承压水的行为对于高级应用的开发是重要的，但是在结构上设计这些期望的效果取决于孔壁的复杂性。金属有机纳米管（蒙茨）由于其一维孔结构、可调的结构特征和在水中的相对稳定性，是探测结构特征和纳米约束效应之间关系的最佳材料。该项目的总体假设是，增加孔壁的疏水性将导致水的更多结构有序化和水通过纳米管的更快扩散。 此外，在壁内组合亲水性和疏水性区域将导致纳米孔对水的化学选择性。 在该项目中，蒙茨用于通过以下方式来测试中心假设：1）识别纳米通道内的簇拓扑结构并将水结构与疏水性相关联; 2）描绘疏水性变化与水扩散速率之间的关系;以及3）确定疏水区域的空间变化如何影响水选择性。这项研究有望有助于我们对复杂材料中纳米承压水行为的基本理解。 有了这种系统的理解，这些想法可以转化为其他材料的行为和修改，并可能对我们对纳米承压水的基本理解产生深远的影响，这对材料科学，化学，地质学，工程学和生物学领域的研究人员来说是很有兴趣的。 教育举措将包括复原力方面的具体培训，以及克服未能提高科学领域代表性不足群体的保留率。 这包括本科生和研究生课程的编制，这些课程将免费分发给外地，以接触更广泛的受众。这些努力还将包括评估和评价最佳实践，以进一步了解弹性培训在提高STEM保留率方面的作用。 该项目由材料研究部的固态和材料化学项目支持。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

PART 1: NON-TECHNICAL SUMMARY Water confined in nanosized channels can behave in unexpected ways and controlling this behavior could lead to the development of new materials for water purification applications. The identity of the chemical components that line the interior wall of these nanochannels may be the crucial design principle that can be used to create new materials with controllable water properties. The overall hypothesis for this project is that the identity and placement of the chemical components that make up the channel wall are key to controlling water confined within these spaces. Metal organic nanotubes (MONTs) are used to test this hypothesis because they contain one-dimensional channels, have tunable channel walls, and exhibit stability in water. Within this project, supported by the Solid State and Materials Chemistry program within the Division of Materials Research, MONTs are designed with chemical components that will either attract or repel the water molecules in specific locations along the interior wall. Then the behavior of the confined water within these new materials is explored by identifying how the confined water molecules are organized within the channel, measuring the rate of water movement through the channels, and testing the ability of the MONTs to selectively take up water over other molecules. Gaining this fundamental knowledge of confined water is important for creating advanced materials for water purification and treatment. Additional educational initiatives for this project include training in resiliency and overcoming failure to improve retention of students in science. This includes curriculum development at both the undergraduate and graduate level that will be freely disseminated to others in the field. These efforts will also include assessment and evaluation of best practices to further our understanding of the role of resiliency training in improving STEM retention. PART 2: TECHNICAL SUMMARY Predicting and controlling the behavior of nanoconfined water is important for the development of advanced applications, but structurally engineering these desired effects are dependent on the complexity of the pore walls. Metal organic nanotubes (MONTs) are optimal for probing the relationships between structural features and nanoconfinement effects due to their 1-D pore structure, tunable structural features, and relative stability in water. The overall hypothesis for this project is that increasing the hydrophobicity of the pore wall will lead to more structural ordering of the water and faster diffusion of water through the nanotube. Furthermore, combining hydrophilic and hydrophobic regions within the walls will lead to chemical selectivity of the nanopore to water. Within this project, MONTs are used to test the central hypotheses through 1) identifying clusters topologies within nanochannels and relating water structure with hydrophobicity; 2) delineating the relationship between variability hydrophobicity and water diffusion rates; and 3) determining how spatial variability of hydrophobic regions impacts water selectivity. The proposed research is expected to contribute to our fundamental understanding of the behavior of nanoconfined water in complex materials. With this systematic understanding, these ideas are translatable to the behavior and modification of other materials and may have far-reaching effects on our fundamental understanding of nanoconfined water, which is of interest to researchers in the fields of material science, chemistry, geology, engineering, and biology. Education initiatives will include specific training in resiliency and overcoming failure to improve retention of underrepresented groups in science. This includes curriculum development at both the undergraduate and graduate level that will be freely disseminated to the field to reach a broader audience. These efforts will also include assessment and evaluation of best practices to further our understanding of the role of resiliency training in improving STEM retention. This project is supported by the Solid State and Materials Chemistry program in the Division of Materials Research.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.