Visible light triggered exfoliation of COF micro/nanomotors for efficient photocatalysis

We report a new facile light-induced strategy to disperse micron-sized aggregated bulk covalent organic frameworks (COFs) into isolated COFs nanoparticles. This was achieved by a series of metal-coordinated COFs, namely COF-909-Cu,-Co or-Fe, where for the first time the diffusio-phoretic propulsion was utilized to design COF-based micro/nanomotors. The mechanism studies revealed that the metal ions decorated in the COF-909 backbone could promote the separation of electron and holes and trigger the production of sufficient ionic and reactive oxygen species under visible light irradiation. In this way, strong light-induced self-diffusiophoretic effect is achieved, resulting in good dispersion of COFs. Among them, COF-909-Fe showed the highest dispersion performance, along with a drastic decrease in particle size from 5 mm to 500 nm, within only 30 min light irradiation, which is inaccessible by using traditional magnetic stirring or ultrasonication methods. More importantly, benefiting from the outstanding dispersion efficiency, COF-909-Fe micro/nanomotors were demonstrated to be efficient in pho-tocatalytic degradation of tetracycline, about 8 times faster than using traditional magnetic stirring method. This work opens up a new avenue to prepare isolated nanosized COFs in a high-fast, simple, and green manner. (c) 2021 Institute of Process Engineering, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communi-cations Co., Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

We developed a light-induced strategy to disperse aggregated bulk covalent organic frameworks (COFs) into isolated COF nanoparticles. Metal-coordinated COFs, specifically COF-909-Cu, -Co, or -Fe, were used to design COF-based micro/nanomotors. Metal ions decorated in the COF-909 backbone promoted electron-hole separation and triggered the production of ionic and reactive oxygen species under visible light irradiation, resulting in efficient dispersion of COFs. Among them, COF-909-Fe showed the best dispersion performance and significantly reduced particle size, leading to enhanced photocatalytic degradation efficiency for tetracycline.