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Superhydrophobic Covalent Organic Frameworks Prepared via Pore Surface Modifications for Functional Coatings under Harsh Conditions

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posted on 2019-12-03, 15:14 authored by Na Han, Zongxuan Zhang, Hongkun Gao, Yongqiang Qian, Linli Tan, Chao Yang, Haoran Zhang, Zhenyu Cui, Wei Li, Xingxiang Zhang
Covalent organic frameworks (COFs) have been widely used in catalysis, energy storage, environmental protection, and separation. However, they require a long assembly period (∼3 days) and complex synthesis conditions; differences in water resistance have restricted their overall versatility. In this paper, the preparation of COF-DhaTab was optimized, and this process can be easily performed in air. Thus, it is feasible for the scale-up of COF-DhaTab in the near future. The superhydrophobic properties of COF-DhaTab (water contact angle, >150°) can be created by regulating the wettability of COF-DhaTab by grafting fluoride. When the grafting degree of fluoride increased to 4.32%, the water contact angle of COFs increased from 0° to more than 150°. The grafted COFs are termed COF-DhaTab fluoride (COF-DTF). The chemically modified COF-DhaTab maintains its original porosity and crystallinity. The superhydrophobic COF-DTF can be applied to various substrates, for example, foam, fabric, and glass. These all exhibit outstanding water repellency, self-healing, and excellent self-cleaning. Importantly, the coating maintains its original superhydrophobicity even under extremely acidic/basic conditions (pH = 1–14) and toward boiling water (100 °C). Furthermore, COF-DTF displays long-term stability and is easily scaled. It is a promising and practical candidate for hydrophobic modifications to various substrates.

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