CAREER: Defining Intrinsic Photophysical and Photocatalytic Properties of Zeolitic Imidazolate Frameworks

金属有机框架是一类新兴的纳米多孔晶体材料，由金属离子或与有机配体配位的团簇组成。在固态和材料化学项目的支持下，黄博士将专注于一种有前途的金属有机框架的基本设计和研究，这种框架具有固有的光活性，即光活性沸石咪唑酸框架（ZIFs）。这些材料在光催化反应和太阳能转化中具有潜在的催化剂应用前景。黄博士和她的团队旨在揭示这些材料未知的光物理和光化学性质，并将这些性质与它们的催化功能直接联系起来，从而在可持续能源的多孔材料领域开辟新的研究方向。此外，拟议的研究将作为提高对全球能源生产和消费关键问题的认识的基础，并将有助于培养下一代太阳能科学家，这是该研究计划长期成功和可持续能源领域持续发展的关键。沸石咪唑盐框架（ZIFs）是一种新兴的金属有机框架，在多相催化中的作用主要是作为分散催化物种的简单宿主或惰性介质。受顺磁性过渡金属的ZIFs在紫外可见-近红外区广泛吸收的启发，该研究小组假设ZIFs可以用作内在光催化材料而不是惰性宿主。NSF CAREER项目的目标是通过阐明zif的光物理和结构/功能关系以及其光催化应用所必需的性质来充分验证这一假设。该项目的重点是阐明光收集、电荷分离、光催化性质的分子水平起源的基本理解，以及控制这些过程效率的因素，该项目的新见解将对未来开发用于光催化和太阳能转换的高效稳定的zif具有巨大价值。具体目标是：i)使用先进的时间分辨光学和x射线瞬态吸收光谱在分子水平上揭示ZIF框架的光学和结构动力学；Ii)系统探索骨架尺寸和化学成分，揭示宏观结构与微观性质的相关性；iii)在框架中封装各种发色团，以增强zif的光收集和光催化性能；iv)将这些光物理性质与所设计的zif的光催化性能相关联，以确定这些多孔材料中的结构-功能关系。

Non-Technical DescriptionMetal organic frameworks are an emerging class of nanoporous crystalline materials consisting of metal ions or clusters coordinated to organic ligands. With support from the Solid State and Materials Chemistry program, the Principal Investigator's NSF CAREER grant Dr. Huang will focus on the fundamental design and investigation of a promising type of metal organic framework, which possesses intrinsic photoactivity, i.e. photoactive zeolitic imidazolate frameworks (ZIFs). These materials have potential applications as catalysts in photocatalytic reactions and solar energy conversion. Dr. Huang and her team aim to uncover the unknown photophysical and photochemical properties of these materials and directly correlate these properties with their catalytic functions, thus initiating a new research direction in the field of porous materials for sustainable energy. Furthermore, the proposed research will serve as a basis to raise awareness around the critical issues of global energy production and consumption, and will help train the next generation of solar energy scientists, which are key to the long-term success of this research program and the continued development of the sustainable energy field.Technical DescriptionThe role of zeolitic imidazolate frameworks (ZIFs), an emerging subclass of metal organic frameworks, in heterogeneous catalysis has largely been to act as a simple host or inert medium for dispersing the catalytic species. Inspired by the broad absorption in UV-visible-near IR region of ZIFs with paramagnetic transition metals, this research team hypothesizes that ZIFs could be used as intrinsic photocatalytic materials rather than as inert hosts. The goals of this NSF CAREER project are to fully test this hypothesis through elucidating the photophysical and structure/function relationships of ZIFs, properties essential for their photocatalytic applications. With its focus on elucidating the fundamental understanding of the molecular-level origins of light harvesting, charge separation, photocatalytic properties, and the factors that control the efficiency of these processes, the new insights from this project will be of immense value to the future development of efficient and stable ZIFs for photocatalysis and solar energy conversion. Specific objectives are: i) using the advanced time-resolved optical and X-ray transient absorption spectroscopy to reveal the optical and structural dynamics of ZIF frameworks at the molecular level; ii) systematically exploring framework dimension and chemical composition to reveal the correlation of macroscopic structure to their microscopic properties; iii) encapsulating various chromophores in the framework to enhance the light harvesting and photocatalytic properties of ZIFs; and iv) correlating these photophysical properties with the photocatalytic performance of the designed ZIFs to determine the structure-function relationship in these porous materials.