Polymorphism of 2D Imine Covalent Organic Frameworks

• Published in: Angewandte Chemie International Edition Vol. 60; no. 10; pp. 5363 - 5369
• Main Authors: Li, Yusen, Guo, Linshuo, Lv, Yongkang, Zhao, Ziqiang, Ma, Yanhang, Chen, Weihua, Xing, Guolong, Jiang, Donglin, Chen, Long
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.03.2021
• Edition: International ed. in English
• Subjects: Benzene; Computer applications; controllable growth; covalent organic frameworks; Growth patterns; Isomers; Monomers; Perturbation; Polymorphism; Query languages; Selective adsorption; Solvents; Symmetry; Vitamin B12; selective adsorption; covalent organic frameworks; isomers; controllable growth
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202015130

We designed and synthesized A2B2 type tetraphenyl benzene monomers (p‐, m‐, and o‐TetPB) which have the para‐, meta, and ortho‐substituted isomeric structures, for the direct construction of isomeric frameworks. Interestingly, both kagome (kgm) and monoclinic square (sql) framework isomers are produced from either p‐TetPB (C2h symmetry) or m‐TetPB (C2v symmetry) by changing reaction solvents, while their isomeric structures are characterized by X‐ray diffraction, computational simulation, microscopy, and sorption isotherm measurements. Only sql frameworks was formed for o‐TetPB (C2v symmetry), irrespective of reaction solvents. These results disclose a unique feature in the framework structural formation, that is, the geometry of monomers directs and dominates the lattice growth process while the solvent plays a role in the perturbation of chain growth pattern. The isomeric frameworks exhibit highly selective adsorption of vitamin B12 owing to pore shape and size differences. A strategy was developed for selective growth of isomeric covalent organic frameworks by designing monomer isomers and tuning reaction conditions. Three A2B2 type tetraphenyl benzene monomers (p‐, m‐, and o‐TetPB) afford five different 2D TetPB‐COF isomers that exhibit selective adsorption of vitamin B12 owing to a great difference in their pore shape and size.