School of Materials Science and Engineering, Experimental Center for Advanced Materials, Beijing Institute of Technology, Beijing 100081, China.
J Phys Chem Lett. 2021 Jul 29;12(29):6767-6772. doi: 10.1021/acs.jpclett.1c01750. Epub 2021 Jul 15.
Porous organic polymers (POPs) have aroused great and wide attention from the materials community, while the identification of their precise structures is still very challenging. The well-defined structures are of great importance in understanding the relationship between the structure and function of the polymer materials, though they are sometimes ignored and do not receive enough attention. In this letter, an efficient N labeling technique and N solid-state NMR (N-SSNMR) were combined to obtain strong evidence for the presence of the azo bond and keto-hydrazone structure in the solid state. Thus, the structure of tris(β-hydroxyl-azo)-benzene in previously proposed hydroxylazobenzene polymers was revised to tris(β-keto-hydrazo)-cyclohexane in TKH-POPs for the first time. In contrast, similar tautomerization did not occur in the azo coupling polymerization of 1,3,5-triaminobenzene and diazonium salts, i.e., tris(β-amino-azo)-benzene remained in Azo-POPs. This work will open up a window to develop innovative porous organic polymers more efficiently with the aid of N-SSNMR.
多孔有机聚合物（POPs）引起了材料界的极大关注，而其精确结构的鉴定仍然具有很大的挑战性。尽管明确的结构对于理解聚合物材料的结构与功能之间的关系很重要，但有时会被忽视，没有得到足够的重视。在这封信中，我们结合了一种有效的 N 标记技术和 N 固体核磁共振（N-SSNMR），在固态中获得了偶氮键和酮腙结构存在的有力证据。因此，首次将先前在羟基偶氮苯聚合物中提出的三（β-羟基偶氮）-苯的结构修订为 TKH-POPs 中的三（β-酮腙）-环己烷。相比之下，在 1,3,5-三氨基苯和重氮盐的偶氮偶联聚合中没有发生类似的互变异构，即 Azo-POPs 中的三（β-氨基偶氮）-苯仍然存在。这项工作将为借助 N-SSNMR 更有效地开发创新的多孔有机聚合物开辟一个窗口。
