关键词: 共价有机框架, 膜材料, 结构设计, 制备方法, 水处理

Abstract: In recent years, with the rapid development of global industrialization, the pollutants contained in industrial wastewater are toxic and difficult to degrade, which seriously affects human health. Covalent organic frameworks (COFs), a new type of porous framework material connected by strong covalent bonds, have attracted wide attention in the fields of photocatalysis, sensing, adsorption and separation, drug delivery and energy storage due to their low density, high porosity, good stability and modifiable framework structure. With the deepening of research, it is found that the use of COFs materials with dense pore structure and surface charge properties can remove pollutants such as textile dyes, toxic heavy metals and salt ions in wastewater, and the effect is better than that of some commonly used filter materials on the market, showing a broad application prospect in the field of sewage treatment.
Currently, there are many kinds of COFs materials, and the differences in internal groups and chemical bonds make their properties different. In the field of water treatment, imine or triazine COFs materials prepared by solvothermal synthesis or ionothermal synthesis are usually selected. Although the crystallinity of such COFs materials is low, the internal stable chemical bonds can keep them stable in water. According to the principle of topological structure design, COFs materials with different pore structures were prepared. Using the regular frame structure of COFs, the performance of COFs materials was improved by functional modification, which greatly expanded its application field. Traditional COFs materials which are mostly powder are difficult to recycle and easy to cause secondary pollution. Changing the use form of COFs materials is the main method to solve this problem. At present, aerogels and separation membranes based on COFs materials have been prepared. Membrane materials are widely used in the field of water treatment because of their recyclability, low energy consumption and high compatibility. The membrane material prepared based on COFs improves the performance and solves the problem that COFs powder is not easy to recycle.
At present, composite membranes and mixed matrix membranes based on COFs have been prepared, showing excellent results in the field of water treatment. Based on the pore size of the membrane, the interception of pollutants is a common method in sewage treatment. The dense pore structure of COFs membrane can intercept dye molecules, heavy metal ions and salt ions in water. Adsorption is another common method in wastewater treatment. The high specific surface area of COFs membrane makes it have excellent adsorption capacity. At the same time, the functional modification of the frame structure can change the surface charge of the membrane and improve its adsorption capacity for pollutants with different ionic properties. And the introduction of hydrophobic or hydrophilic groups inside the framework can also make the COFs membrane have the ability of oil-water separation.
The effect of COFs materials in the field of water treatment shows that they have great application potential in this field. Expanding the form of COFs, and improving performance and expanding application fields through functional modification are the research hotspots of COFs materials. However, there are few types of COFs materials suitable for water treatment, and the current preparation yield of COFs materials is low. Therefore, it is necessary to increase the research on the synthesis of COFs materials, explore and find COFs materials suitable for water treatment, and promote the development of water treatment.

Key words: covalent organic frameworks, membrane materials, structural design, preparation methods, water treatment