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。新材料往往表现出独特的性质，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，或者开发用于医疗或环境应用的新传感器。石墨烯的发展是一种新材料的一个突出例子，它重新定义了现有的应用，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组合成复合材料，其中多种材料的性能可以组合在一个结构中。除了简单地结合单个材料的性能外，复合材料往往会产生全新的性能，超过任何一种成分的性能。要发现新的复合材料，我们需要了解它们是如何形成的，并利用这一知识来种植可以设计成具有理想性能的复合材料。该项目旨在将两种有前景的材料组合成新的复合结构：多孔石墨烯材料和二维共价有机骨架(2D-COF)。2D-COF是通过共价键将独立的分子构件连接在一起来创建扩展的二维分子结构而形成的。本课题所研究的2D-COF是表面负载的卟啉2D-COF。这意味着2D-COF的生长发生在下表面，主要分子成分是卟啉分子。卟啉是用途广泛、用途广泛的有机分子成分。卟啉在生物系统、光合作用和红细胞中结合氧的重要作用以及在催化剂和传感器中的技术作用证明了它们提供化学功能的潜力。我将使用一种名为石英晶体微天平(QCM)的实验工具来实时跟踪2D-COF在多孔石墨烯材料上的生长。将通过缩合反应在分子之间形成共价键来生长卟啉2D-COF。这些缩合反应释放水分子，与此相关的质量变化可以通过QCM检测到。这些现场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，该项目将研究在高比表面积石墨烯材料上的生长，如石墨烯泡沫和石墨烯水凝胶。2D-COF应用的一个主要障碍是它们在恶劣条件下缺乏稳定性。为了生产有序的2D-COF，有必要使用共价键将分子可逆地连接在一起。如果键是不可逆的，则生长的2D-COF中的缺陷被捕获，并产生无序结构。然而，使用可逆键形成过程的一个限制是，尽管得到的2D-COF是有序的，但它们也容易降解，使它们不适合在恶劣环境中需要稳定性的应用。该项目旨在开发生长后化学处理，以增加预先形成的卟啉2D-COF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来向预制的2D-COF添加功能的方法。这些构建块将具有在2D-COF生长过程中不活跃的化学基团，但随后可用于将其他功能成分，如染料分子或纳米颗粒，连接到预制的2D-COF上。这种模块化的方法使用2D-COF作为模板来制备复杂和功能材料。该项目将导致对功能有机纳米结构的生长的新的理解，以及一套具有广泛应用潜力的新的复合材料。

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.