Light-driven MOF-based micromotors with self-floating characteristics for water sterilization

Abstract

Three-dimensional motion (especially in the Z-axis direction) of metal–organic frameworks (MOFs)-based micromotors (MOFtors) is essential but still in its infancy. Herein, we propose a simple strategy for designing light-driven MOFtors that move in the Z-axis direction and efficiently kill Staphylococcus aureus (S. aureus). The as-prepared polypyrrole nanoparticles (PPy NPs) with excellent photothermal properties are combined with ZIF-8 through a simple in situ encapsulation method, resulting in multi-wavelength photothermally-responsive MOFtors (PPy/ZIF-8). Under the irradiation of near-infrared (NIR)/ultraviolet (UV)/blue light, the MOFtors all exhibited negative phototaxis and high-speed motion behaviour with the highest speed of 2215 ± 338 μm s⁻¹. In addition, it is proved that these MOFtors can slowly self-float up in an aqueous environment. The light irradiation will accelerate the upward movement of the MOFtors, and the time required for the MOFtors to move to the top is negatively correlated with the light intensity. Finally, efficient antibacterial performances (up to 98.89% against S. aureus) are achieved with these light-driven MOFtors owing to the boosted Zn²⁺ release by vigorous stirring motion and physical entrapment by the upward motion under light irradiation.