N-Doping Carbon-Nanotube Membrane Electrodes Derived from Covalent Organic Frameworks for Efficient Capacitive Deionization.

Capacitive deionization (CDI) is an energy-efficient and environmentally friendly electrochemical desalination technology which has attracted increasing attention in recent years. Electrodes are crucial to the performance of CDI processes, and utilizing a carbon-nanotubes (CNTs) membrane to fabricate electrodes is an attractive solution for advanced CDI processes. However, the strong hydrophobicity and low electrosorption capacity limit applications of CNTs membranes in CDI. To solve this problem, we introduce crystalline porous covalent organic frameworks (COFs) into CNTs membranes to fabricate N-doping carbon-nanotubes membrane electrodes (NCMEs). After solvothermal growth and carbonization, CNTs membranes are successfully coated with imine-based COFs and turned into integrated NCMEs. Comparing with the CNTs membranes, the NCMEs exhibit an ∼2.3 times higher electrosorption capacity and superior reusability. This study not only confirms that COFs can be used as high-quality carbon sources but also provides a new strategy to fabricate high-performance CDI electrodes.