Creating molecular networks with different topologies using identical molecular linkers is fundamentally important, but requires a precise chemistry control. Here, we propose an effective strategy to regulate network topologies of two-dimensional (2D) covalent organic frameworks (COFs) through conformation switching of molecular linkages. By simply altering the substituents of an identical molecular linker, the topology-selective synthesis of two highly crys-talline 2D COFs can be readily achieved. Their distinct crystal structures are observed and determined by low-dose high-resolution transmission electron microscopy imaging, indicating that the driving force for linkage conformation switching is intramolecular hydrogen bonding. Our strategy would greatly diversify the COF topologies and enable vast post-synthetic modifications like boron complexation, endowing these structures with unique optical property, such as fluorescence “turn on” and “aggregation-induced emission”.
|Original language||English (US)|
|Journal||Journal of the American Chemical Society|
|State||Published - Jul 4 2020|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work was supported by MOE under AcRF Tier 2 (MOE2016-T2-2-103; MOE2017-T2-1-162) in Singapore. Y. Zhu acknowledges the financial support from the National Natural Science Foundation of China (Grant No. 21771161) and Thousand Talents Program for Distinguished Young Scholars. We would like to acknowledge the Facility for Analysis, Characterization, Testing and Simulation, Nanyang Technological University, Singapore, for use of their electron microscopy (and/or X-ray) facilities. H.Z. thanks the financial support from ITC via Hong Kong Branch of National Precious Metals Material Engineering Research Center (NPMM), and the start-up grant (Project No. 9380100) and grants (Project No. 9610478 and 1886921) in City University of Hong Kong.