CAREER: Understanding and Ccontrolling Fatigue in Photo-Responsive MOFs: Characterizing Photochromic Transformations in Single Crystals

非技术摘要：在材料研究部固态材料化学项目资助的这个项目中，研究小组正在开发可被紫外光激活的结晶多孔材料。光活性化学基团在暴露于光时改变形状。这些光驱动的转化导致晶体框架的孔（洞）和通道改变形状，导致能够选择性地吸收或释放客体分子（例如药物）的材料，但仅当暴露于适当波长的光时。除了推进我们对这些新型材料中发生的基本光化学的理解外，该研究还建立了设计原则，以了解并最终控制和防止各种光响应材料的疲劳（失效）。教育和推广活动通过继续为高年级本科生和研究生开发X射线科学课程，将晶体学和X射线科学带入美国课堂。教育项目，包括全国范围内的晶体生长的竞争，带来晶体和光的概念，K-12教室通过实践实验和课程开发的教师和学生的发展。技术摘要：本研究的重点是识别和理解疲劳的根本原因，在光致变色材料与开发设计原则，以控制任何光响应系统的疲劳的最终目标。主要目标是开发一个详细的分子水平的理解内发生的光化学二芳基乙烯基材料，一个令人兴奋的利基在新生领域的光响应金属有机框架。 研究的具体目标包括：（1）新的基于二芳基乙烯的光可切换连接体和由这些连接体制备的金属有机框架的合成和表征，（2）使用光谱和衍射方法定量结晶环境中光致变色分子的光物理学以确定反应能量学和限制，（3）确定控制这些材料中疲劳的因素和触发因素，（4）开发新技术以评估金属-有机骨架纳米孔内客体物质的分布并确定它们对结晶骨架的光物理性质的影响，（5）使用所获得的知识来合理设计和工程化具有增强的性质（即改善的抗疲劳性）的先进光致变色材料。主要研究工具包括传统和原位单晶X射线衍射（光晶体学），稳态和时间分辨吸收光谱/显微镜，核磁共振（NMR），质谱，热重分析和计算建模。

Non-technical Abstract:In this project funded by the Solid-State Materials Chemistry program of the Division of Materials Research, the research team is developing crystalline porous materials that are activated by UV light. The photo-active chemical groups change shape when exposed to light. These light-driven transformations cause the pores (holes) and channels of the crystalline frameworks to change shape leading to materials capable of selectively absorbing or releasing guest molecules, for example pharmaceutical drugs, but only when exposed to the proper wavelength of light. In addition to advancing our understanding of the fundamental photochemistry that occurs in these novel materials, the research establishes design principles to understand and ultimately control and prevent fatigue (failure) in a variety of photo-responsive materials. The education and outreach activities bring crystallography and X-ray science into U.S. classrooms through the continued development of an X-ray science course for advanced undergraduate and graduate students. The educational projects, including a nation-wide crystal growing competition, bring concepts of crystals and light to K-12 classrooms through the development of hands-on experiments and curricular development for teachers and students.Technical Abstract:This research focuses on identifying and understanding the root causes of fatigue in photochromic materials with the ultimate goal of developing design principles to control fatigue in any photo-responsive system. The primary objective is developing a detailed molecular level understanding of the photochemistry occurring within diarylethene-based materials, an exciting niche in the nascent field of photo-responsive metal-organic frameworks. Specific aims of the research include: (1) the synthesis and characterization of new diarylethene-based photoswitchable linkers and metal-organic frameworks prepared from these linkers, (2) quantifying the photophysics of photochromic molecules in crystalline environments using spectroscopic and diffraction methods to determine reaction energetics and limitations, (3) determining the factors and triggers that govern fatigue in these materials, (4) developing new techniques to assess the distribution of guest species within the metal-organic framework nanopores and determining their impact on the photophysical properties of the crystalline frameworks, (5) using the knowledge gained to rationally design and engineer advanced photochromic materials with enhanced properties, namely improved resistance to fatigue. The primary research tools include traditional and in situ single crystal X-ray diffraction (photo-crystallography), steady-state and time-resolved absorption spectroscopy/microscopy, nuclear magnetic resonance (NMR), mass spectrometry, thermogravimetric analysis, and computational modeling.