Constructing ordered and tunable extrinsic porosity in covalent organic frameworks via water-mediated soft-template strategy

• Published in: Nature communications Vol. 15; no. 1; p. 3896
• Main Authors: He, Ningning, Zou, Yingdi, Chen, Cheng, Tan, Minghao, Zhang, Yingdan, Li, Xiaofeng, Jia, Zhimin, Zhang, Jie, Long, Honghan, Peng, Haiyue, Yu, Kaifu, Jiang, Bo, Han, Ziqian, Liu, Ning, Li, Yang, Ma, Lijian
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 08.05.2024; Nature Publishing Group; Nature Portfolio
• Subjects: 140/131; 140/133; 147/135; 147/143; 639/301/357/1018; 639/301/923/1028; 639/638/298/923/1028; Accessibility; Chemical bonds; Covalence; Crystallization; Functional groups; Guanidine; Humanities and Social Sciences; Incompatibility; Ion exchange; Mass transfer; multidisciplinary; Porosity; Porous materials; Science; Science (multidisciplinary); Self-assembly; Synthesis
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-48160-0

As one of the most attractive methods for the synthesis of ordered hierarchically porous crystalline materials, the soft-template method has not appeared in covalent organic frameworks (COFs) due to the incompatibility of surfactant self-assembly and guided crystallization process of COF precursors in the organic phase. Herein, we connect the soft templates to the COF backbone through ionic bonds, avoiding their crystallization incompatibilities, thus introducing an additional ordered arrangement of soft templates into the anionic microporous COFs. The ion exchange method is used to remove the templates while maintaining the high crystallinity of COFs, resulting in the construction of COFs with ordered hierarchically micropores/mesopores, herein named OHMMCOFs (OHMMCOF-1 and OHMMCOF-2). OHMMCOFs exhibit significantly enhanced functional group accessibility and faster mass transfer rate. The extrinsic porosity can be adjusted by changing the template length, concentration, and ratio. Cationic guanidine-based COFs (OHMMCOF-3) are also constructed using the same method, which verifies the scalability of the soft-template strategy. This work provides a path for constructing ordered and tunable extrinsic porosity in COFs with greatly improved mass transfer efficiency and functional group accessibility. The synthesis of covalent organic frameworks (COFs) by a soft-template methodology is challenging. Here, the authors attach the soft templates to the COFs backbone via ion bonds, avoiding crystallization incompatibilities and allowing subsequent removal of the template by ion exchange for enhanced U(VI)/Th(IV) adsorption performance.