光响应二维COF的设计合成与主客体化学

Single-layer two-dimensional covalent organic frameworks (2D COFs), in which internal structures introduce photosensitive groups, are structurally adaptable in response to external stimuli have attracted great attention due to their potential applications as stimuli-responsive smart materials. So far, the researches in this area mainly focused on constructing 2D COFs in a well-defined arrangement, few examples concerning the functional 2D COFs have been reported. In this project, we design and synthesize a series of photoresponsive 2D COFs containing azobenzene moieties based on surface-confined Schiff-base coupling, boronic acid self-condensation and boronate esterification reaction. Their photoisomerization behaviors will be investigated by scanning tunneling microscope (STM) on the highly oriented pyrolytic graphite (HOPG) surface. The functionalized 2D COFs are expected to exhibit fully reversible responsive pore size by using UV irradiation and thermal treatment. Therefore, the photoresponsive 2D COF containing azobenzene moieties, in which trans-to-cis isomerization can induce the opening and closing of 2D COF cavities, further realize the controlling capture and release of targeted guests by using these crystalline porous surface COFs as nanopatterning. A combination of photo-induced stimuli-responsive 2D COF and host–guest chemistry may lead to potentially applications in the field of molecular switch, nanopatterning and nanofilters.

通过引入光活性官能团可实现单层二维有机共价框架（2D COFs）对外界刺激的响应性，因二维COF在智能材料等方面具有潜在的应用前景而备受关注。目前这方面的研究工作主要集中在高覆盖度且结构有序二维COF的构筑，单层二维COF的功能化仍处于探索阶段。本项目利用表面限域的席夫碱反应、硼酸自缩合和硼酸酯化反应，通过在单体上引入偶氮苯官能团设计并合成一系列光响应二维COF，借助扫描隧道显微镜（STM）在高定向热解石墨（HOPG）表面研究它们的光致异构化行为。通过紫外辐照和热处理，利用偶氮苯反式-顺式异构化诱导二维COF空腔的打开与闭合，实现功能化二维COF空腔的完全可逆的调控；进一步以二维COF为纳米模板实现对客体分子的可控捕获与释放。光诱导的响应性2D COF和主客体化学的结合为实现其在分子开关、纳米模板和纳米过滤器等领域的应用提供了可能。

共价有机框架（COF）是一类通过共价键连接而成的有机材料，具有优异的稳定性、高比表面积和易于修饰化的特点，尤其是含有光响应性基团的共价有机框架材料的设计、合成以及功能化应用备受关注。本研究基于表面限域的席夫碱反应、硼酸自缩合和硼酸酯化反应，通过引入含偶氮苯官能团设计合成一系列共价有机框架材料，利用扫描隧道显微镜研究其在高定向热解石墨表面的自组装的行为，揭示表面自组装化学反应机制以及探索特殊浸润性共价有机材料在含油废水处理领域方面的应用。项目按照研究计划顺利进行，已按要求完成项目内容。基于席夫碱反应和烯烃复分解反应，利用两步法，通过调节反应温度、时间、催化剂、浓度等条件，实现了高产率刚性大环制备，揭示了双烯单体表面自组装动态共价化学机制，为发展超分子化学理论奠定了坚实基础。基于席夫碱反应，通过在室温条件下分子表面自组装反应，调控反应物浓度、温度、催化剂等实验产生，实现了共价有机聚合物微球的可控构筑。以二维铜网为基底，通过席夫碱反应，优化实验参数（温度、底物浓度、时间、催化剂），实现了超疏水油水混合溶液的快速高效分离（＞99%，油通量＞65 L•m-2•s-1），同时还展现出良好的循环稳定性。通过水热法在纤维织物上发生席夫碱反应，调控实验参数，在纤维织物上构筑微纳米结构和疏水化学组成，实现含偶氮基团共价有机聚合物修饰的超疏水二维纤维织物的制备，证实了该材料具有高效（＞99%）的水包油乳液的分离性能，为共价有机框架纳米材料在油水分离提供了新思路。