Porous Molecular Crystals and Metal-Organic Frameworks Based on Fluorinated Pyrazoles

非技术摘要多孔材料的结构中有微小的空洞。由于这些孔洞在尺寸上与分子相当，所以多孔材料在能源、石油化工、环境和医学等领域得到了广泛的应用。在材料研究部固态和材料化学计划的支持下，该项目开发了以单个分子为构件的新型多孔材料。与目前可用的多孔材料相比，这类材料具有更好的性能：它们重量轻、可回收，而且更容易加工，因为它们是可溶的，原则上可以在表面上“涂抹”。它们不同寻常的内部结构使这些材料成为极好的防水剂；它们还能够捕获氟里昂和氟碳化合物--这两种物质都是强大的温室气体和臭氧消耗物质。此外，它们强烈地结合了碳氢化合物，这使得它们在燃料储存和漏油清理方面的应用前景光明。这项研究项目与一个广泛的教育计划相结合，旨在提高学生在能源和可持续发展领域的能力，并让本科生和高中生参与原创研究，重点是少数族裔和女性学生。技术摘要这个合作项目的重点是制备基于吡唑类化合物的广泛氟化的多孔材料。含氟金属有机骨架是通过将吡唑类化合物去质子化成吡唑类化合物并与过渡金属配位而形成的。氟化吡唑类化合物被选为配体，因为它们的高碱度应该转化为化学上坚固的骨架。含氟分子晶体是由中性含氟吡唑通过[pi···pi]堆积和氢键结合在一起形成的多孔骨架自组装而成。这些多孔分子晶体是最近由主要研究人员发现的。这项研究填补了现有知识的一个空白：由于缺乏适当的氟化分子前体，广泛的氟化多孔材料一直没有得到充分的探索。本项目将通过其四个目标极大地扩大这一领域的知识：(1)制定通过新型铜和钯催化的C-H官能化反应获得广泛含氟的芳香族吡唑(及其衍生物)的一般合成战略；(2)将含氟的吡唑类化合物网状形成多孔分子晶体，并了解产生持续高于200℃的孔隙率所必需的结构元素；(3)从拟议工作的第一部分中制备的吡唑类前体配体开始合成广泛含氟的金属-有机骨架；(4)对两类含氟材料进行详尽的表征，着眼于未来的应用。所关注的性能特征包括：(A)氟里昂和氟碳化合物、(B)含氟麻醉剂、(C)两亲性含氟污染物、(D)碳氢化合物和(E)分子氧的热稳定性和化学稳定性、疏水性以及作为吸附剂的潜力。这项研究在有机金属、无机和超分子化学领域产生了基本的新知识。

Non-technical abstractPorous materials have microscopic voids in their structures. Because these voids are comparable in dimensions to molecules, porous materials find numerous applications related to energy, petrochemical industry, environment, and medicine. With the support of the Solid State and Materials Chemistry program in the Division of Materials Research, this project develops new classes of porous materials in which building blocks are individual molecules. Such materials have superior properties relative to the currently available porous materials: they are lightweight, recyclable, and much more easily processable, as they are soluble and can in principle be "painted" on a surface. Their unusual internal structures make these materials superb water-repellants; they are also capable of capturing Freons and fluorocarbons-which are both powerful greenhouse gases and ozone-depleting substances. In addition, they strongly bind hydrocarbons, which makes them promising in applications in fuel storage and oil spill cleanup. This research project is integrated with a broad education plan that aims to increase student competency in the areas of energy and sustainability, as well as to involve undergraduate and high school students in original research, with a focus on minority and female students.Technical abstractThis collaborative project is focused on the preparation of extensively fluorinated porous materials based on pyrazoles. Fluorinated metal-organic frameworks are formed by deprotonation of pyrazoles into pyrazolates and their coordination to transition metals. Fluorinated pyrazolates have been chosen as ligands since their high basicity should translate into chemically robust frameworks. Fluorinated molecular crystals are formed by the self-assembly of neutral fluorinated pyrazoles into a porous framework held together by a combination of [pi···pi] stacking and hydrogen bonding. These porous molecular crystals were recently discovered by the principal investigators. This research fills a gap in the existing knowledge: extensively fluorinated porous materials have been underexplored because of the paucity of the appropriately fluorinated molecular precursors. This project will dramatically expand the knowledge in this area, through its four goals: (1) creation of a general synthetic strategy to access extensively fluorinated aromatic pyrazoles (and derivatives) through novel copper- and palladium-catalyzed C-H functionalization reactions; (2) reticulation of fluorinated pyrazoles into porous molecular crystals, and understanding of structural elements necessary for the creation of robust porosity that persists above 200 °C; (3) synthesis of extensively fluorinated metal-organic frameworks starting from the precursor pyrazolate ligands prepared in the first part of the proposed work, and (4) exhaustive characterization of both classes of fluorinated materials, with an eye toward future applications. Performance characteristics of interest include: thermal and chemical stability, hydrophobicity, and potential as adsorbents for (a) Freons and fluorocarbons, (b) fluorinated anesthetics, (c) amphiphilic fluorinated pollutants, (d) hydrocarbons, and (e) molecular oxygen. This research generates fundamental new knowledge in the areas of organometallic, inorganic, and supramolecular chemistry.