CAREER: Two-Dimensional Covalent Organic Framework (2D COF) Membranes: A New Platform for Liquid Separations

液体分离通过用于处理饮用水、制造疗法和净化工业化学品，对国家的健康和繁荣至关重要。目前实现这些液体分离的方法面临着高能耗、低生产率和不完美的分离性能的挑战。共价有机骨架是具有有序多孔结构的聚合物，可以作为膜有效地分离复杂的液体，如从水中去除盐或从有机液体中过滤杂质。这项研究项目将设计具有可调孔特性的超薄共价有机骨架膜，以实现基于液体特定特性的液体分离。在设计共价有机骨架膜性能方面所获得的基础知识将使它们能够被专门设计来实现更有效的液体分离，用于能源、环境和健康领域的应用。该研究计划与职前科学和数学教师的专业发展相结合，他们将从事个人研究项目，并将为他们通常服务的公立高中开发基于探究的课程。本研究的目标是设计具有可调孔特性的二维共价有机骨架(2D COF)膜，并基于尺寸、电荷和吸附对其液体分离性能进行建模。通过在受限界面上对正交可溶单体进行界面聚合，可以制备出不同厚度的大面积膜。通过在可控界面聚合过程中将可变长度的单体直接集成到2D COF中，以及通过引入空间位阻来设计2D COF单分子层的堆积，可以实现对2D COF孔结构的控制。通过制造后的化学官能化对孔表面进行修饰，将能够控制孔化学。2DCOF膜的分离性能将用于有机混合物和水溶液，包括有机溶剂纳滤、微咸水淡化和铀吸附。实验结果将被用于开发和验证包括空间和非空间机理的二维COF膜分离的孔流模型。来自TETHHOUSTON项目的八名职前中学STEM教师将通过开展个人研究项目和开发相关STEM课程来从事研究。这些项目旨在培养探究思维，并为职前教师在大休斯顿地区的公立高中实施基于探究的STEM课程做好准备。研究成果还将被整合到膜分离研究生课程中，这将有助于缩小对来自不同化学和工程领域的分离科学家的培训差距。将开展水处理学习活动，向更广泛的社区介绍新的过滤概念，并激发人们对分离科学的兴趣。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。

Liquid separations are central to the health and prosperity of the nation through their use in treating drinking water, manufacturing therapeutics, and purifying industrial chemicals. Current approaches to achieve these liquid separations are challenged by high energy consumption, low production rates, and imperfect separation performance. Covalent organic frameworks are polymers with ordered porous structures that can function as membranes to efficiently separate complex liquids, such as removing salt from water or filtering impurities from organic liquids. This research project will engineer ultrathin covalent organic framework membranes with tunable pore properties to achieve liquid separations based on specific characteristics of the liquids. The fundamental knowledge that is gained about engineering the properties of covalent organic framework membranes will enable them to be specifically designed to achieve more effective liquid separations for applications in the energy, environmental, and health fields. The research program is integrated with the professional development of pre-service science and math teachers who will engage in individual research projects and will develop inquiry-based curriculum for the public high schools in which they typically serve.The goal of this research is to engineer two-dimensional covalent organic framework (2D COF) membranes with tunable pore properties and to model their performance for liquid separations based on size, charge, and adsorption. Large-area membranes with varying thicknesses will be fabricated by interfacial polymerization of orthogonally soluble monomers at a confined interface. Control over 2D COF pore structure will be achieved by direct integration of variable-length monomers into 2D COFs during their controlled interfacial polymerization and by engineering the stacking of 2D COF monolayers through introduced steric hindrances. Pore surface modifications by post-fabrication chemical functionalization will enable control over pore chemistry. The separation performance of the resulting 2D COF membranes will be tested for organic mixtures and aqueous solutions, including organic solvent nanofiltration, brackish groundwater desalination, and uranium adsorption. The experimental results will be used to develop and validate pore-flow models for 2D COF membrane separations that include steric and non-steric mechanisms. Eight pre-service secondary STEM teachers from the teachHOUSTON program will engage in the research by conducting individual research projects and developing related STEM curriculum. The projects are designed to cultivate an inquiry mindset and prepare the pre-service teachers to enact inquiry-based STEM curriculum in public high schools in the greater Houston area. The research results will also be integrated into a Membrane Separations graduate course that will help close the gap in training for separation scientists from disparate chemistry and engineering fields. A water treatment learning activity will be developed to introduce new filtration concepts to the broader community and to stimulate interest in separation science.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.