离子骨架二维共价有机多孔框架材料及其膜的设计合成与其选择性离子传输性质研究

The transport of ions in porous materials is a fundamental physicochemical process that is widely involved in many real-world applications such as molecular adsorption/separation, water purification, electrochemical capacitive energy storage, and catalyst and fuel cells. Current ion transport membranes, like sulfonated (DuPont Nafion) or quaternary ammoniated membrane, have low ion selectivity, high cost and very low chemical stability, proven to be induced by their ion exchange groups. Indeed, most pure polymer porous membranes showed a relatively poor performance due to the conflict between ion selectivity and conductivity. To address this challenge, we introduce ionic two-dimensional covalent organic framework (2D COF) materials as ideal membrane for ultrafast ion transport and separation. COFs are a class of porous polymer in which organic building blocks are precisely integrated into extended structures with periodic skeletons and ordered pores. 2D COFs have a well-defined alignment of π building units in their atomic layers and segregated arrays of π columns in their frameworks. The elegant π skeletons of 2D COFs provide a fundamental basis for structural design. Meanwhile, the sizes, shapes and environments of their 1D channel are fully controllable. In this project, we will explore ionic 2D COF for high permeability and high selectivity ion transport as followings: (1) synthesizing numerous ionic 2D COF with different pore size and electric density for ion transport, screening stable COF for ions separation applications; (2) explore new strategies to prepare ionic 2D COF membranes for ions separation. Meanwhile, we will study the ion transport properties of COF membranes and analyze the ion separation mechanism based on the research results with the help of theoretical simulations. Through the implementation of this project, it is expected to provide the theoretical and experimental information for the fabrication of ion transport membrane based on 2D COFs.

离子选择性传输在水纯化、离子筛分、燃料电池、电化学能量存储等中具有重要的意义。为了解决传统的离子膜在离子传输过程中存在的离子选择性和渗透性之间的矛盾，本项目以高效选择性离子传输通道的构筑为导向，拟利用二维共价有机多孔框架（Covalent Organic Frameworks，COFs）材料孔隙率高、孔道结构有序、结构易调控等特点，通过分子设计制备具有直通有序离子传导通道的离子骨架二维COF材料，系统研究材料纳米孔道限域传质效应和骨架电荷密度对离子传输行为的影响规律。初步探索离子骨架二维COF膜材料的可控制备，以具有代表性的应用领域（燃料电池、锂离子电池等）为方向，研究离子骨架二维COF膜对特定离子的传输机理。通过本项目实施，以期获得二维COF材料中离子选择性传输的过程机理和强化途径，突破传统膜离子选择性和渗透性的博弈问题，为实现基于二维COF材料的高效选择性离子传输提供理论和实验基础。

离子传输是一个重要的物理化学过程。选择性离子传输通道的构建在水纯化、离子分离、燃料电池、电化学能量存储等中都占据了重要位置。传统的高分子离子交换膜在离子传输过程中存在的离子选择性和渗透性之间的矛盾。因此构筑高效率选择性离子传输膜需要在分子设计和离子传输机理上作进一步的完善。本项目以高选择性离子传输通道的构筑为导向，通过制备具有离子交换功能的单体，合成孔道带电荷的离子型共价有机多孔框架（Covalent Organic Frameworks，COFs）材料，利用COF材料纳米孔道的筛分作用来提高膜的离子选择性，同时其带电荷孔道限域传质作用来增加膜的离子传输效率，从而解决传统高分子膜通过增加离子交换基团来提高离子传导率的束缚。.在本项目的资助下，我们设计合成了系列离子型共价有机多孔框架材料如阳离子COF膜（EB-COF：Br），阴离子COF膜（TpPa-SO3Na）和同时具备阴、阳离子官能团的两性离子型共价有机骨架（Zwitterionic COFs）材料，并详细探讨了其电荷控制的离子传输和无水质子传导性能。其中，以两性离子COF为主体负载三氮唑、咪唑等质子载体，相反电荷的组合赋予了两性离子COF丰富的离子迁移位点，使其在负载三氮唑、咪唑后实现了优异的无水质子传导性能（4.38×10-2 S/cm，413 K）。我们将质子解离能理论计算与频率相关的介电分析相结合，进一步深入了解了离子COF材料中孔道尺寸和电荷密度对提高质子传导和离子选择性传输性能的作用。同时，我们深入研究了纳米孔限阈作用耦合电场控制的离子传输性能在凝胶电解质锂离子电池和Li离子电池中的应用潜力。相关工作发表SCI论文13篇，其中影响因子10以上5篇，包括ACS Nano(1), JMCA(2), Chemical Engineering Journal(2), ACS Appl. Mater. Interfaces(4)等。申请发明专利5项，其中已有2项获得授权。