Metal–organic frameworks (MOFs) have potential uses in environmental remediation (i.e., the removal of pollutants). They can, for example, adsorb pollutants such as organic compounds or metals. Bubble propulsion is a promising alternative to mechanical stirring to increase the exposure of the MOF to the pollutants in aqueous solutions. However, it is challenging to design bubble-propelled MOF micromotors (MOFtors) with small MOF particle sizes.
Yulong Ying, Sheng Wang, Zhejiang Sci-Tech University, Hangzhou, China, and colleagues have developed a universal and straightforward strategy to efficiently self-assemble Fe-UIO nanoparticles—Fe3O4 nanoparticles combined with the MOF NH2-UiO-66—into robust colloidosomes (Fe-UIOSomes). Colloidosomes are microcapsules whose shells are composed of colloidal particles.
The Fe-UIOSomes were self-assembled using a so-called transient Pickering emulsion method (pictured below). In this method, Fe-UiO NPs were dispersed in an aqueous phase after ultrasonic treatment, and then the aqueous droplets were suspended in n-butanol under the action of a high-speed shearing machine. The water then gradually diffuses into the n-butanol phase and the desired Fe-UiOSomes are formed.
The Fe-UIOSomes were decorated with platinum nanoparticles by chemical reduction of a platinum salt to form Fe-UiOSomes-Pt motors (MOFbots). When exposed to hydrogen peroxide, the platinum nanoparticles generate oxygen bubbles, which propel the MOFbots with speeds up to 450 µm s–1 (pictured at the top). Pollutants such as chromium(VI) were reduced by 91 % when using the MOFbots. According to the researchers, this is comparable to the performance achieved by mechanical shaking.
- Large‐Scale Self‐Assembly of MOFs Colloidosomes for Bubble‐Propelled Micromotors and Stirring‐Free Environmental Remediation,
Hai Huang, Jie Li, Mengge Yuan, Haowei Yang, Yu Zhao, Yulong Ying, Sheng Wang,
Angew. Chem. Int. Ed. 2022.
Update (October 13, 2022)
The image has been updated with one with higher resolution and more explanation.