Asymmetric Assembly in Microdroplets: Efficient Construction of MOF Micromotors for Anti‐Gravity Diffusion

Abstract

AbstractJanus‐micromotors, as efficient self‐propelled materials, have garnered considerable attention for their potential applications in non‐agitated liquids. However, the design of micromotors is still challenging and with limited approaches, especially concerning speed and mobility in complex environments. Herein, a two‐step spray‐drying approach encompassing symmetrical assembly and asymmetrical assembly is introduced to fabricate the metal‐organic framework (MOF) Janus‐micromotors with hierarchical pores. Using a spray‐dryer, a symmetrical assembly is first employed to prepare macro‐meso‐microporous UiO‐66 with intrinsic micropores (<0.5 nm) alongside mesopores (≈24 nm) and macropores (≈400 nm). Subsequent asymmetrical assembly yielded the UiO‐66‐Janus loaded with the reducible nanoparticles, which underwent oxidation by KMnO4 to form MnO2 micromotors. The micromotors efficiently generated O2 for self‐propulsion in H2O2, exhibiting ultrahigh speeds (1135 µm s−1, in a 5% H2O2 solution) and unique anti‐gravity diffusion effects. In a specially designed simulated sand‐water system, the micromotors traversed from the lower water to the upper water through the sand layer. In particular, the as‐prepared micromotors demonstrated optimal efficiency in pollutant removal, with an adsorption kinetic coefficient exceeding five times that of the micromotors only possessing micropores and mesopores. This novel strategy fabricating Janus‐micromotors shows great potential for efficient treatment in complex environments.