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 μm 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 photocatalytic 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.