Simple and Continuous Fabrication of Self-Propelled Micromotors with Photocatalytic Metal-Organic Frameworks for Enhanced Synergistic Environmental Remediation

This work reports on a simple and general strategy for continuous fabrication of self-propelled micromotors with photocatalytic metal-organic frameworks (MOFs) for enhanced synergistic degradation of organic contaminants. With emulsion microdroplets from microfluidics as templates, uniform porous micromotors decorated with Fe3O4@Ag nanoparticles (Fe3O4@AgNPs) at the bottom and zeolitic imidazolate framework-8@ZnO nanoparticles (ZIF-8@ZnONPs) on the surface can be synthesized. The spatial location of ZIF-8@ZnONPs and Fe3O4@AgNPs in micromotors is accurately controlled in one step via their directional migration in the confined microspace of emulsion droplets driven by interfacial energy and magnetic field. The nanoengines Fe3O4@AgNPs enable asymmetric decomposition of H2O2 for bubble-propelled motion and easy magnetic recycling of the micromotor. The porous structures of micromotors provide a large surface area, benefiting decoration of Fe3O4@AgNPs and their contact with H2O2 for promoting bubble generation and reduced micromotor weight for promoting bubble-propelled motion. The nanophotocatalysts ZIF-8@ZnONPs allow enrichment of organic contaminant molecules via adsorption for efficient photocatalytic degradation. With synergistic coupling of the photocatalysis of ZIF-8@ZnONP5 and advanced oxidation of the H2O2/UV system, the micromotors with bubble-propelled motion for improved mixing can achieve enhanced degradation of organic contaminants via dual synergistic degradation mechanisms. As highlighted by degradation of rhodamine B, the micromotors exhibit the highest degradation performance as compared to control groups with a single degradation mechanism and with dual degradation mechanisms but without self-propelled motion. This simple fabrication strategy is general and can be flexibly extended to other MOF materials, which may open up new avenues for developing advanced MOF-integrated micromotors for myriad applications.