Hydrophobic covalent organic frameworks: a green synthesis approach for efficient oil/water separation

Rapid economic development has led to oil pollution and energy shortage. Thus, it is highly desirable to develop an efficient and environment-friendly approach for oil/water (O/W) separation. Herein, we report a simple and green method for preparing macroscopic COF AG and AG. COF AG was rapidly synthesized at room temperature, washed and freeze-dried to prepare COF AG without any adhesives or additives. Due to its strong hydrophobicity, COF AG is used as an absorbent for removing organic pollutants in O/W separation, and has a certain demulsification performance, which has a certain application prospect in the field of O/W separation. The hydrophobic COF AG material was combined with MA, which was synthesized in one step at room temperature, avoiding the long reaction conditions of traditional high temperature and high-pressure reaction, as well as the post-modification process and complex washing steps. The superhydrophobic sponge material was rapidly prepared. The introduction of MA reduced the amount of COF monomer, improved the adsorption capacity of the material for organic solvents and oil samples, increased from 37 times of the previous maximum adsorption weight to more than 120 times, and the demulsification capacity of O/W emulsion increased to more than 99%, with the ability of direct separation and continuous separation of O/W. Therefore, the prepared superhydrophobic sponge has high adsorption capacity and good reusability, and can be used for O/W separation. This work not only provides a strategy for the construction of functional COF, but also opens up a way for the growth of COF on different carriers for O/W separation.