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Covalent organic frameworks (COFs) are constructed from small organic molecules through reversible covalent bonds, and are therefore considered a special type of polymer. Small organic molecules are divided into nodes and connectors based on their roles in the COF’s structure. The connector generally forms reversible covalent bonds with the node through two reactive end groups. The adjustment of the length of the connector facilitates the adjustment of pore size. Due to the diversity of organic small molecules and reversible covalent bonds, COFs have formed a large family since their synthesis in 2005. Among them, a type of COF containing redox active groups such as –C=O–, –C=N–, and –N=N– has received widespread attention in the field of energy storage. The ordered crystal structure of COFs ensures the ordered arrangement and consistent size of pores, which is conducive to the formation of unobstructed ion channels, giving these COFs a high-rate performance and a long cycle life. The voltage and specific capacity jointly determine the energy density of cathode materials. For the COFs’ cathode materials, the voltage plateau of their active sites’ VS metallic lithium is mostly between 2 and 3 V, which has great room for improvement. However, there is currently no feasible strategy for this. Therefore, previous studies mainly improved the theoretical specific capacity of the COFs’ cathode materials by increasing the number of active sites. We have summarized the progress in the research on these types of COFs in recent years and found that the redox active functional groups of these COFs can be divided into six subcategories. According to the different active functional groups, these COFs are also divided into six subcategories. Here, we summarize the structure, synthesis unit, specific surface area, specific capacity, and voltage range of these cathode COFs.

Carbendazim, belonging to fungicides, was commonly used for controlling crop diseases, resulting in frequent residues in fruits and vegetables. Washing was the initial step of household fruit processing for cleaning and reducing pollutant contents. However, the effect of washing on the removal of carbendazim in apples was not systemically studied. Thus, in this study, an analytical method was firstly established for the determination of carbendazim with great accuracy and precision through quick, simple, cheap, effective and safe (QuEChERS) method and ultra-performance liquid chromatography-fluorescence detection (UPLC-FLD). Then, the influencing factors were systematically researched to unveil their effects on the carbendazim residue in apples. The results indicated that water temperature, washing products and washing method could obviously affect the carbendazim content in apples. In addition, the best cleaning scheme for removal of carbendazim was soaking apples for 5 min in a cleaning solution, which was prepared by dissolving 8 g of commercial fruit washing soup with 500 ml of water 3145. Under this condition, the removal rate of carbendazim in the washing step reached 73.91%. This study will be helpful for providing guidance for household cleaning methods for controlling pesticide residues. [ABSTRACT FROM AUTHOR]

Tea infusion is the main route of human exposure to pollutants in tea, and it is vital to investigate the transfer rate of pollutants from tea leaves to infusion. Carbendazim is a commonly used systemic fungicide, the transfer behavior of which in Yingshan Yunwu tea is not clear. Hence, this study firstly established the analytical method for determination of carbendazim with great accuracy and precision via modified QuEChERS method and ultra-performance liquid chromatography-fluorescence detection (UPLC-FLD). Then, the transfer behavior of carbendazim from tea leaves and infusion was systematically investigated. Results indicated that water temperature and proportion of tea to water ration would obviously increase the transfer rate of carbendazim, but times of infusion repetition showed negative correlation with the transfer rate of carbendazim. In addition, brewing time seemed to have lesser impact on the transfer rate. This study will be helpful for the risk assessment of carbendazim residue and provide the guidance for tea brewing. [ABSTRACT FROM AUTHOR]