An Innovative, Unorthodox, and General Strategy for the Synthesis of Zeolitic-Imidazolate Framework (ZIF) Membranes for Olefin/Paraffin Separations

[1132157] jeong .提出的工作目标是开发一种创新的、非正统的、通用的策略，以商业上可行的方式合成金属-有机框架（特别是沸石-咪唑盐框架）膜，用于高分辨率分离烯烃/石蜡混合物，如丙烯/丙烷和乙烯/乙烷。沸石咪唑盐框架（ZIFs）是金属有机框架（mof）的一个亚类，由于其超微孔（孔径小于5 Å）、独特的热/化学稳定性以及无与伦比的框架灵活性，为气体分离提供了独特的机会。例如，在zif中，基于气体溶解度和扩散率差异的基本分离机制可以通过所谓的闸门打开效应（更广泛地称为呼吸效应）来控制，其中特定分子的吸附和扩散可以通过阈值压力（即柔性框架）来调节。由于这些阈值压力因不同的气体分子而异，因此zif在分离应用中具有极大的灵活性。然而，许多阻碍沸石膜更广泛地应用于商业应用的基本挑战仍然存在于ZIF膜中。这些挑战包括缓慢的批次结晶、晶界缺陷和昂贵的多孔支架。此外，不同拓扑结构的沸石膜通常是通过试错法合成的，再现性仍然是一个主要问题。为了充分利用这类新兴的纳米多孔框架材料用于膜基气体分离的潜力，需要开发一种完全不同的策略。许多从事MOF膜研究的研究人员都有沸石膜的背景，因此他们试图应用与过去相同的技术和经验。相比之下，PI提出了一种独特的视角来合成ZIF膜，打破了传统的想法。关键的假设是，由于这些材料的化学性质与沸石的化学性质根本不同，因此可以开发出一种完全不同的合成MOF膜的转变方法。提出的工作将建立在快速热沉积（RTD）技术在PI的小组开发。该计划有三个主要目标：1)基于RTD技术开发一种创新的、非正统的、通用的合成策略；2)表征和控制ZIF膜的微观结构；3)测试膜的性能。本文提出的创新策略将以前所未有的方式适用于任何MOF膜的大规模合成，从而有可能使其实际应用成为现实。这项工作将使PI能够确定基于快速热沉积的转化合成策略是否可以成功地开发用于ZIF膜。提出的基础研究将导致一套设计规则，用于快速合成任何具有独特微观结构的ZIF膜。ZIF膜的微观结构（特别是晶界缺陷）将首次被表征，然后控制以最大限度地提高分离性能。ZIF的骨架柔韧性对孔隙和晶界结构的影响将被确定，这将反过来决定ZIF膜的性能。能够进行烯烃/石蜡分离的膜的开发将导致一种比目前的蒸馏实践消耗更少能源的技术，从而留下更小的碳足迹。虽然这项工作的重点是烯烃/石蜡的分离，但这里研究的材料及其膜将与化学和石化工业面临的其他困难的分离有关。这项工作的跨学科性质，跨越材料设计和合成，表征，膜制造和测试，将为参与的学生（一名研究生和一名REU本科生）带来真正的多学科研究经验。以本研究为基础的科学视频教育推广活动的开发将通过提高公众对科学和工程的兴趣，对K-12教育产生积极的影响。

1132157JeongThe goal of the proposed work is to develop an innovative, unorthodox, and general strategy to synthesize metal-organic framework (specifically zeolitic-imidazolate framework) membranes in a commercially viable manner for high resolution separations of olefin/paraffin mixtures such as propene/propane and ethene/ethane. Zeolitic imidazolate frameworks (ZIFs), a subclass of metal-organic frameworks (MOFs), offer unique opportunities in gas separations due to their ultra-micropores (pores smaller than 5 Å), their unique thermal/chemical stabilities, and their unparalleled framework flexibilities. For example, in ZIFs, the fundamental separation mechanism based on the differences in the solubilities and the diffusivities of gases can be controlled due to a so called gate-opening effect (more broadly known as a breathing effect) in which the adsorption and diffusion of specific molecules can be regulated by threshold pressures (i.e., flexible frameworks). Since these threshold pressures vary for different gas molecules, ZIFs possess tremendous flexibility for separation applications. However, many of the fundamental challenges hindering zeolite membranes from being more widely used in commercial applications still remain for ZIF membranes. These challenges include slow batch crystallization, grain boundary defects, and expensive porous supports. Additionally, zeolite membranes of different topology are often synthesized by trial-and-error approaches and reproducibility is still a major problem. A fundamentally different strategy needs to be developed in order to fully harvest the potential of this emerging class of nanoporous framework materials for membrane-based gas separations. Many researchers working on MOF membranes come from a zeolite membrane background and thus try to apply the same techniques and experiences that they have used in the past. In contrast, the PI proposes to take a unique perspective on the synthesis of ZIF membranes that breaks away from conventional thought. The key hypothesis is that a radically different transformative approach to synthesizing MOF membranes can be developed due to the fact that the chemistry of these materials are fundamentally different from zeolite chemistry. The proposed work will be built upon the rapid thermal deposition (RTD) technique developed in the PI's group. The proposed plan has three main objectives: 1) development of an innovative, unorthodox, and general synthesis strategy based on the RTD technique, 2) characterization and control of ZIF membrane microstructure, and 3) testing of membrane performance. The innovative strategy proposed here will be applicable for the large-scale synthesis of any MOF membrane in an unprecedented manner, thereby potentially rendering their practical applications a reality. This work will enable the PI to determine if a transformative synthesis strategy based on rapid thermal deposition can be successfully developed for ZIF membranes. The proposed fundamental research will lead to a set of design rules for the rapid synthesis of any ZIF membrane with a unique microstructure. ZIF membrane microstructures (in particular, grain boundary defects) will be characterized for the first time and then controlled to maximize separation performance. The effects of the ZIFs' framework flexibility on the pore and grain boundary structures will be determined which will in turn determine the performance of the ZIF membranes. The development of membranes capable of performing olefin/paraffin separations will lead to a technology that consumes less energy than the current practice of distillation, thereby leaving a much smaller carbon footprint. While the focus of this work is olefin/paraffin separations, the materials and their membranes investigated here will be relevant to other difficult separations facing the chemical and petrochemical industries. The interdisciplinary nature of the work, spanning material design and synthesis, characterization, and membrane fabrication and testing, will lead to a truly multidisciplinary research experience for the students (one graduate and one REU undergraduate) involved. The educational outreach activity development of science videos based on the proposed research will positively impact K-12 education by increasing public interest in science and engineering.