In-situ studies of the growth of two-dimensional covalent organic frameworks

新材料的开发在现有技术的发展中起着至关重要的作用。新材料通常显示出独特的性能，这些性能为解决重要的社会问题提供了新的方法，例如制造更好的催化剂或开发用于医疗或环境应用的新传感器。石墨烯的发展是新材料的一个突出例子，它重新定义了现有的应用，并在许多情况下提出了全新的应用。开发新材料的一种行之有效的方法是将不同的结构联合收割机组合成复合材料，其中多种材料的性能可以组合在单一结构中。除了简单地将单个材料的性能结合起来之外，复合材料通常会产生超越任何一种成分的全新性能。为了发现新的复合材料，我们需要了解它们是如何形成的，并利用这些知识来生长可以设计成具有理想性能的复杂材料。该项目旨在将两种有前途的材料联合收割机组合成新的复合结构：多孔石墨烯材料和二维共价有机框架（2D-COFs）。2D-COF是通过用共价键将单独的分子结构单元连接在一起以产生扩展的二维分子结构而形成的。本项目研究的二维COFs是表面负载卟啉二维COFs。这意味着2D-COF的生长发生在下面的表面上，并且主要的分子组分是卟啉分子。卟啉是用途广泛的有机分子化合物。卟啉在生物系统、光合作用和红细胞中的氧结合以及催化剂和传感器技术中的重要作用证明了卟啉提供化学功能的潜力。我将使用一种称为石英晶体微天平（QCM）的实验工具来实时跟踪多孔石墨烯材料上2D-COFs的生长。卟啉2D-COF将使用缩合反应生长以形成分子之间的共价连接。这些缩合反应释放出水分子，与此相关的质量变化可以通过QCM检测到。这些原位测量将使我们能够深入了解环境条件（如温度压力和湿度）如何影响2D-COF结构的生长。利用这些见解，我将找到2D-COF生长的最佳条件，该项目将研究高表面积石墨烯材料（如石墨烯泡沫和石墨烯水凝胶）的生长。2D-COF应用的主要障碍是它们在恶劣条件下缺乏稳定性。为了产生有序的2D-COF，必须使用将分子可逆地连接在一起的共价键。如果键是不可逆的，则在生长的2D-COF中的缺陷被捕获并且产生无序结构。然而，使用可逆键形成方法的限制在于，虽然所得2D-COF是有序的，但它们也易于降解，使得它们不适合于需要在恶劣环境中稳定性的应用。该项目旨在开发生长后的化学处理，以增加预形成的卟啉2D-COFs的稳定性，同时保持其有序结构。最后，还将研究通过使用定制设计的分子构建块向预形成的2D-COF添加功能的方法。这些结构单元将具有在2D-COF生长期间无活性的化学基团，但随后可用于将其他功能组分（例如染料分子或纳米颗粒）连接到预形成的2D-COF。该模块化方法使用2D-COFs作为模板来生产复杂的功能材料。该项目将导致对功能有机纳米结构生长的新理解，以及一系列具有广泛应用潜力的新复合材料。

The development of new materials plays a vital role in the evolution of existing technology. New materials often display unique properties that suggest new ways of solving important societal problems such as making better catalysts or the development of new sensors for medical or environmental applications. The development of graphene is a prominent example of a new material that redefined existing applications and in many cases suggested entirely new ones. A proven approach to developing new materials is to combine different structures to form composite materials where the properties of multiple materials can be combined in a single structure. In addition to simply combining the properties of individual materials, composite materials often lead to entirely new properties that surpass those of either of the components.To discover new composite materials we need to understand how they form and utilise this knowledge to grow complex materials that can be designed to have desirable properties. This project aims to combine two promising types of materials into new composite structures: porous graphene materials and two-dimensional covalent organic frameworks (2D-COFs). 2D-COFs are formed by linking separate molecular building blocks together with covalent bonds to create extended two-dimensional molecular structures. The 2D-COFs studied in this project are surface supported porphyrin 2D-COFs. This means the growth of the 2D-COF takes places on an underlying surface and the main molecular components are porphyrin molecules. Porphyrins are highly versatile and widely used organic molecular components. The potential of porphyrins to provide chemical functionality is demonstrated by their important roles in biological systems, photosynthesis and binding oxygen in red blood cells and technologically in catalysts and sensors.I will use an experimental tool called a quartz crystal microbalance (QCM) to track the growth of 2D-COFs on porous graphene materials in real-time. Porphyrin 2D-COFs will be grown using a condensation reaction to form the covalent links between molecules. These condensation reactions release water molecules and the mass change associated with this can be detected by QCM. These in-situ measurements will allow us to gain insights into how environmental conditions, such as temperature pressure and humidity, influence the growth of 2D-COF structures. Using these insights I will find optimal conditions for 2D-COF growth and the project will investigate the growth on high surface area graphene materials such as graphene foams and graphene hydrogels.A major obstacle to the application of 2D-COFs is their lack of stability in harsh conditions. To produce ordered 2D-COFs it is necessary to use covalent bonds that link molecules together reversibly. If bonds are non-reversible defects in the growing 2D-COF become trapped and disordered structures are produced. However, a limitation to using reversible bond formation processes is that while the resulting 2D-COFs are ordered they are also susceptible to degradation, making them unsuitable for applications that require stability in harsh environments. This project aims to develop post-growth chemical treatments that increase the stability of pre-formed porphyrin 2D-COFs while maintaining their ordered structure. Finally, an approach to adding functionality to pre-formed 2D-COFs by using custom designed molecular building blocks will also be investigated. These building blocks will have chemical groups which are inactive during 2D-COF growth but subsequently can be used to attach other functional components, such as dye molecules or nanoparticles, to the preformed 2D-COFs. This modular approach use 2D-COFs as templates for producing complex and functional materials.This project will lead to a new understanding in the growth of functional organic nanostructures and a new set of composite materials with potential in a wide range of applications.