金属Salen基表面二维有机网格的设计构筑与性能研究

Two-dimensional covalent organic frameworks (2D COFs) are a class of layered materials with high crystallinity and porosity. Due to the diversity of building blocks and the designability of extended structures, 2D COFs are becoming emerging materials for structural control and functional design. However, it remains a great challenge to fabricate 2D COFs with big size domain, high degree of order and controllable number of layers. Moreover, it is also desirable to realize the functionalization of 2D COFs. Considering the above issues, we would like to fabricate on-surface 2D COFs with Salen unit. The porosity and designability of COFs are subtly combined with the multifunctionality of Salen complexes to expand the applications of 2D COFs. The main research contents in this project are as follows: 1) Explore the strategies for one-step synthesis of functional 2D Salen COFs with high quality; 2) By using scanning probing microscopy, the molecular adsorption, assembly and reaction processes would be studied at molecular scale. We intend to explore the influence of temperature, substrate, metal ions and surface coverage on fabrication of 2D Salen COFs systematically, which will be beneficial to understand the mechanism of surface reaction and realize structural regulation and controllable synthesis. 3) Exploit the applications of 2D Salen COFs in electrochemical catalysis and develop the relationship between topological structure of COFs and their performance.

由于组装基元的多样性以及拓扑结构的可设计性，二维共价有机框架材料（2D COFs）正成为一类结构可控制和功能可设计的新兴多孔材料。然而由于反应单体组装构型难于控制、共价键可逆性差等原因，制备高度有序、大面积、层数可控的2D COFs，同时实现其功能化仍然存在很多挑战。本项目以功能为导向，将COFs材料的多孔性、拓扑结构可调节性与金属Salen复合物的功能性相结合，一步制备多孔隙率、高有序度、功能化的表面金属Salen二维有机网格。在发展大面积、高质量表面2D Salen COFs制备方法的同时，借助于扫描探针显微术，从分子水平考察表面2D Salen COFs的组装、反应、生长机制以及共价键与配位键之间的协同、竞争作用对表面COFs生长过程的影响。探索表面有机网格结构与其性能之间的构效关系，为设计构筑高催化活性的表面二维有机网格提供理论依据。

利用分子工程学，从分子水平设计构筑具有特定拓扑结构和功能基元的二维共价有机网格是实现纳米材料功能化的有效方法，该方法具有灵活可控的优点，通过对分子单元的选择和设计，可以实现对网格结构和功能特性的精确调控。本项目主要以二维有机网格为研究对象，在探索网格结构与性能之间的构效关系的同时，借助于扫描探针显微镜，从分子水平上研究二维有机网格的组装生长规律。主要研究内容包括：设计构筑系列Salen型共价有机网格结构，测试其作为二次离子电池负极材料的储能性能，探究储能机理；将具有不同孔径大小的共价有机网格应用于钾离子电池负极材料，提出了多孔结构对钾离子存储行为的尺寸效应；设计构筑具有单分散的金属铼催化位点的二维共价有机网格结构用于光催化二氧化碳还原，负载金属铼的共价有机网格材料不仅表现出比相应的分子催化剂更好的催化效率，而且稳定性高，可以重复多次循环使用；通过调节构筑基元的分子尺寸，选择性调控组装分子共结晶或者相分离；利用外加电场调控不同超分子组装结构之间发生可逆相转变。项目研究成果为从分子尺度合理设计具有特定功能特性的共价有机网格材料，理解网格结构与性能之间的构效关系提供了实验依据，通过本项目的实施，部分研究成果已经在本领域知名国际期刊发表。