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Three-Dimensional Hydrazone-Functionalized Covalent Organic Frameworks as pH-Triggered Rotary Switches

submitted on 04.03.2021, 01:42 and posted on 05.03.2021, 04:07 by Wenjuan Zhao, Chengyang Yu, Fengqian Chen, Xinyu Guan, Hui Li, Bin Tang, Valentin Valtchev, Yushan Yan, Shilun Qiu, Qianrong Fang
The property expansion of three-dimensional (3D) functionalized covalent organic frameworks (COFs) is important for developing their potential applications. Herein, we report the first case of 3D hydrazone-decorated COFs as pH-triggered molecular switches, and explore their application in the stimuli-responsive drug delivery system. These functionalized COFs with hydrazone groups on the channel walls were obtained via a multi-component bottom-up synthesis strategy. They exhibit a reversible E/Z isomerization at various pH values, confirmed by UV-vis absorption spectroscopy and proton conduction. Remarkably, after loading cytarabine (Ara-C) as a model drug molecule, these pH-responsive COFs showed an excellent and intelligent sustained-release effect with an almost 4-fold increase in the Ara-C release at pH = 4.8 than at pH = 7.4, which will effectively improve drug-targeting and reduce drug side effects. Thus, these results open a way toward designing 3D stimuli-responsive functionalized COF materials and promote their potential application as drug carriers in the field of disease treatment.


National Natural Science Foundation of China (22025504, 21621001, and 21390394), 111 project (BP0719036 and B17020), China Postdoctoral Science Foundation (2020TQ0118 and 2020M681034)


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Jilin University



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No conflict of interest