LEAPS-MPS: Mobility and reactivity of covalent organic framework precursors under physical confinement by exfoliated 2D materials

该奖项的全部或部分资金来自《2021年美国救援计划法案》(公共法律117-2)。非技术摘要共价有机骨架(COF)是一种多种多样的结晶二维聚合物，由于组分间成键的几何形状以及反应物分子上存在的键和官能团的性质变化，这些聚合物具有高度可调的性质。在不同的界面上，人们已经研究了“限制下”的COF的形成，但对于被困在两个固体表面之间的反应物，还没有研究过。石墨烯是单层共价连接的碳原子，很容易从石墨中剥离，并能将高流动性的分子捕获到固体表面。通过这项LEAPS-MPS项目，克拉克森大学瑞安·布朗教授的研究小组研究了石墨烯和固体表面之间的捕集反应物，以研究固体-固体界面上COF的形成。他们研究了当反应物被限制在固体界面之间时，COF的生长是如何变化的。由于高温下的竞争反应或脱附，一些COF键不容易通过表面或溶液中的直接缩合反应形成。布朗教授的团队使用石墨烯限制作为执行这些不可访问的反应的策略，以及使用石墨烯捕获来模拟通常不是通过直接缩合反应形成的键的COF增长。除了科学方面，该项目还通过面向终身教职前教师的研讨会邀请，为来自代表不足背景的本科生举办的专业发展研讨会，以及为来自当地土著社区的高中生提供有偿研究经验，在数学和物理领域吸引了代表不足的社区。技术摘要限制在各种界面上的二维共价有机框架(COF)的生长是一个活跃的领域，根据限制的性质，有多种结果。然而，到目前为止，这一领域的现有工作还没有解决在固体-固体界面约束下形成2D-COF的后果。了解限制在固-固界面之间的COF生长对于评估利用这类材料作为插层物种来改变过渡金属二卤化物和MXenes等二维材料的化学、光学或电学性质的可行性是很重要的。在这个LEAPS-MPS项目中，Ryan Brown教授的研究小组通过使用扫描探针显微镜(SPM)、空间分辨傅立叶变换红外光谱(FTIR)和密度泛函理论计算来评估限制在剥离的石墨烯和固体界面之间的COF前体的迁移率和反应性的变化，探索了固体表面之间的物理限制对COF生长的影响。剥离的石墨烯可以将气体、液体和小分子限制在固体界面上，石墨烯-云母和石墨烯-Au(111)界面被用作实验上可访问的固体-固体界面限制的模型系统。布朗教授的研究小组研究了石墨烯覆盖层对单反应物和多反应物体系中常见缩合反应形成的COF的生长和形貌的影响。这项工作还扩展到评估在表面使用石墨烯限制来产生不容易通过直接缩合反应获得的COF连接的可行性。此外，布朗教授与克拉克森大学现有的组织合作，通过一系列丰富的活动和研究机会，加强对数学和物理科学背景较少的本科生和终身教职前教师的指导、培训和职业发展。来自纽约北部土著社区的高中生也通过这个项目获得了宝贵的研究机会和经验。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Non-Technical AbstractCovalent organic frameworks (COFs) are a diverse field of crystalline two-dimensional polymers that have highly tunable properties due to the geometry of the bonding between components and variability in the nature of the bond and functional groups present on the reactant molecules. The formation of COFs “under confinement” has been studied at a variety of interfaces, but not for reactants trapped between two solid surfaces. Graphene is a single layer of covalently linked carbon atoms that is easily exfoliated from graphite and can trap highly mobile molecules at solid surfaces. With this LEAPS-MPS project, Professor Ryan Brown’s research group at Clarkson University investigates trapping reactants between graphene and a solid surface to study COF formation at a solid-solid interface. They look at how COF growth changes when reactants are confined between solid interfaces. Some COF linkages are not easily formed through a direct condensation reaction at surfaces or in solution due to competing reactions or desorption at the high-temperatures. Prof. Brown’s group employes graphene confinement as a strategy for carrying out these inaccessible reactions, as well as using graphene trapping to pattern COF growth for linkages not normally formed through direct condensation reactions. In addition to the science aspects, the project also engages underrepresented communities within the Mathematical and Physical sciences field through seminar invitations for pre-tenure faculty, professional development workshops for undergraduate students from underrepresented backgrounds, and the provision of paid research experience for high school students from the local indigenous communities.Technical AbstractThe growth of two-dimensional covalent organic frameworks (COFs) confined at a variety of interfaces is an active field with a variety of outcomes based on the nature of the confinement. So far though, the existing body of work in this field does not address the consequences of forming 2D-COFs under confinement by a solid-solid interface. Understanding COF growth confined between solid-solid interfaces is important for assessing the viability of employing this class of materials as intercalation species to modify the chemical, optical, or electrical properties of two-dimensional materials such as transition metal dichalcogenides and MXenes. With this LEAPS-MPS project, Professor Ryan Brown’s research group explores the impact of physical confinement between solid surface on COF growth by employing scanning probe microscopy (SPM), spatially-resolved Fourier transform infrared spectroscopy (FTIR), and density functional theory calculations to assess changes in the mobility and reactivity of COF precursors confined between exfoliated graphene and solid interfaces. Exfoliated graphene can confine gases, liquids, and small molecules at solid interfaces, and the graphene-mica and graphene-Au(111) interfaces are used as experimentally accessible model systems for confinement at a solid-solid interface. Professor Brown’s research group investigates the impact of a graphene capping layer on the growth and morphology of COFs formed from common condensation reactions for single and multiple reactant systems. This work also extends to assessing the viability of using graphene confinement at surfaces to produce COF linkages not readily accessible through direct condensation reactions. Additionally, Professor Brown works with existing organizations within Clarkson University to enhance the mentoring, training, and career progression undergraduate students and pre-tenure faculty members from underrepresented backgrounds in Mathematical and Physical Sciences through a series of enrichment activities and research opportunities. High school students from the northern New York indigenous communities gain valuable research exposure and experience through this program, as well.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.