Yan Qianqian, Xu Huanjun, Jing Xuechao, Hu Hui, Wang Shenglin, Zeng Chaoyuan, Gao Yanan
Key Laboratory of Ministry of Education for Advanced Materials in Tropical Island Resources, Hainan University No. 58, Renmin Avenue Haikou 570228 China
School of Science, Qiongtai Normal University China.
RSC Adv. 2020 May 5;10(30):17396-17403. doi: 10.1039/d0ra02142c.
Post-synthetic modification has been the most powerful strategy for covalent organic frameworks (COFs) for their functionalization in many fields. This strategy is typically achieved through the quantitative reaction between existing reactive sites on the linkers (building units) and incoming functional groups. However, usage of linkages (bonds formed to construct COFs) for the post-synthetic modification still remains limited. Herein, we develop a new post-synthetic modification route that is based on the modification of linkages. With this strategy, the imine linkages of a two-dimensional (2D) COF, TFPPy-PyTTA-COF, have been transformed into amine linkages to give the amine-linked isostructure with retention of crystallinity and porosity. The subsequent aminolysis of the amine linkages with 1,3-propane sultone and further metathetical reaction with cobalt acetate [Co(OAc)] enable the introduction of cobalt alkyl sulfonate to the one-dimensional (1D) channel walls of the COF. The resulting ionic COF with coupled Co in the frameworks shows excellent catalytic activity and good recyclability towards the cycloaddition reactions of epoxides and CO. This strategy is of interest as it opens a way to use linkage modification for exploring the potential of COFs for different applications.
后合成修饰一直是共价有机框架（COF）在许多领域实现功能化的最有效策略。该策略通常通过连接体（构建单元）上现有的反应位点与引入的官能团之间的定量反应来实现。然而，用于后合成修饰的连接键（用于构建COF的形成的键）的使用仍然有限。在此，我们开发了一种基于连接键修饰的新的后合成修饰路线。通过这种策略，二维（2D）COF，TFPPy-PyTTA-COF的亚胺连接键已转化为胺连接键，以得到具有结晶度和孔隙率保留的胺连接的同构结构。随后，胺连接键与1,3-丙烷磺酸内酯进行氨解，并与醋酸钴[Co(OAc)]进一步进行复分解反应，从而能够将烷基磺酸钴引入到COF的一维（1D）通道壁中。所得框架中耦合有Co的离子型COF对环氧化物和CO的环加成反应显示出优异的催化活性和良好的可回收性。该策略很有意义，因为它开辟了一条利用连接键修饰来探索COF在不同应用中的潜力的途径。
