The controllable fabrication of asymmetric yolk-shell ZIF-67@PDA as NIR light-driven nanomotor for enhanced selective adsorption

Asymmetrical micro/nanomotors have aroused extensive attention in environmental remediation owing to their inimitable self-propelled characteristic at micro/nanoscale. However, current asymmetrical micro/nanomotors systems are limited by complex synthesis processes and low controllability. Herein, a NIR light propelled asymmetric ZIF-67@PDA nanomotor with eccentric spherical yolk and rhombohedral shell structure was constructed for the enhanced selective adsorption of cationic organic pollutant. The asymmetric ZIF-67@PDA nanomotor was prepared through interfacial growth-etching strategy. The formation mechanism of ZIF-67@PDA was investigated, and the asymmetric yolk-shell structure can be well-controlled through varying reaction time or adjusting the amount addition of dopamine. The asymmetric yolk-shell structured ZIF-67@PDA nanomotors can generate thermal gradient fields with NIR light irradiation, resulting in self-thermophoresis propulsion. Under the NIR light irradiation (808 nm, 3 W/cm2), the translational diffusion coefficient of ZIF-67@PDA nanomotors can reach 39.5 μm2/s and the movement velocity is up to 10.3 μm/s. Moreover, the ZIF-67@PDA nanomotors driven by NIR light exhibit the enhanced selective adsorption for cationic organic pollutant. The removal efficiency of ZIF-67@PDA nanomotors for cationic pollutant methyl blue reaches 85.6 %, while that for anionic pollutant methyl orange is only 21.5 %. Such a design may provide a novel method for the construction of asymmetric structured nanomotors.