Pressure-induced Breathing in Microporous Coordination Polymer Thin Films: A Mechanism for Gas Sensing

在化学系化学测量和成像(CMI)计划的支持下，以及已建立的刺激竞争研究计划(EPSCoR)的部分共同资助下，阿拉巴马大学塔斯卡卢萨分校的Gregory Szulczewski和他的团队正在设计和表征用于薄膜传感器的特殊聚合物，用于检测和定量挥发性有机化合物(VOC)。这项工作旨在更好地理解聚合物膨胀过程与散装固体中的不同之处。这些见解将反过来应用于新型气体传感器技术的开发，如果成功，将有可能在环境、工业和农业领域应用。该项目将吸引K-12年级的学生，试图激励他们考虑学习科学；活动将包括科学演示和在当地科学博物馆和学校开展的动手活动。暑期研究项目计划吸引HBCU(历史上的黑人学院和大学)的学生，他们寻求科学、技术、工程和数学方面的职业生涯。微孔配位聚合物，或MCP，已成为催化、气体储存、气体分离和化学传感的潜在材料。对这些应用至关重要的是材料定义良好的孔隙率。在一些情况下，结构是刚性的，但一些MCP表现出呼吸现象，其中晶格膨胀可以发生在给定VOC的一定压力之上，允许客体快速扩散到新修饰的微孔主体中。Szulczewski小组的目标是确定呼吸MCP薄膜合成的关键设计参数，并建立关键的结构-功能关系，这将促进对晶格膨胀的基本理解。具体地说，该团队将测量VOCs在“呼吸”MCP薄膜中的吸附/解吸等温线，以确定“开门”压力。他们将进一步探索不同的MCP构建块(即金属离子和有机连接物)的影响，以及缺陷、薄膜厚度和一般形貌对晶格膨胀机制的作用。使用并行阻抗测量和迭代反馈回路，这些基础研究的目标是开发一种新型的气体传感器技术。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Measurement and Imaging (CMI) Program in the Division of Chemistry, and partial co-funding from the Established Program to Stimulate Competitive Research (EPSCoR), Gregory Szulczewski and his group at the University of Alabama - Tuscaloosa are designing and characterizing special polymers intended for use in thin-film sensors for detection and quantitation of volatile organic compounds (VOCs). The work seeks better understanding of how the polymer swelling process differs from that in bulk solids. These insights in turn will be applied to the development of a new type of gas sensor technology, that, if successful, has potential for applications in the environmental, industrial, and agricultural sectors. The project will engage K-12 students, seeking to motivate them to consider studying science; activities will include scientific demonstrations and hands-on activities conducted at a local science museum and schools. Summer research projects are planned to engage students from HBCUs (Historically Black Colleges and Universities) who seek careers in science, technology, engineering and math.Microporous coordination polymers, or MCPs, have emerged as potential materials for catalysis, gas storage, gas separations, and chemical sensing. Critical to these applications is the well-defined porosity of the material. In some instances the structure is rigid, but some MCPs exhibit a breathing phenomenon, wherein lattice expansion can occur above a certain pressure of a given VOC, allowing rapid diffusion of the guest into the newly modified microporous host. The Szulczewski group aims to identify key design parameters for the synthesis of breathing MCP thin films and to establish the key structure-function relationships that will advance the basic understanding of lattice expansion. Specifically, the team will measure adsorption/desorption isotherms of VOCs in thin films of “breathing” MCPs to identify the “gate-opening” pressure. They will further probe the impact of varying MCP building blocks (i.e., metal ions and organic linkers) as well as the role of defects, film thickness, and general morphology on the mechanism of lattice expansion. Using parallel impedance measurements and an iterative feedback loop, these fundamental studies are targeting development of a new type of gas sensor technology.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.