Size-controlled cuboctahedral HKUST-1-modified hollow MnO2 micromotors for adsorptive capture and catalytic degradation of organic pollutants

Size-controlled cubic–octahedral HKUST-1 is synthesized for modifying both inner and outer walls of hollow microtubes. • The Mn 3 O 4 -derived MnO 2 @HKUST-1 hollow composite micromotor integrates pollutant adsorption-enrichment with redox-mediated catalytic degradation within a unified platform. • Controlled HKUST-1 crystal size and deposition enabled uniform coating on hollow MnO₂ microtubes, enhancing pollutant enrichment while preserving catalytic sites and self-propulsion. In this study, cotton was employed as a biological template, and a size-controlled octahedral HKUST-1 structure was constructed via a combined calcination and hydrothermal process. Subsequently, a hollow tubular MnO 2 @HKUST-1 composite micromotor, derived from Mn 3 O 4 , was successfully fabricated. Under H 2 O 2 -driven conditions, the as-prepared micromotor exhibits stable autonomous motion and enables efficient removal of methylene blue (MB). Under optimized reaction conditions, a 90.4% removal efficiency was achieved within 10 min, and complete degradation was reached within 40 min. Kinetic and mechanistic analyses indicate that HKUST-1 primarily contributes to pollutant enrichment via its porous structure, whereas MnO 2 is responsible for H 2 O 2 activation and reactive oxygen species (ROS) generation. This work, for the first time, proposes a structural design principle for MOF-based micromotors that differs fundamentally from conventional MOF-coating strategies. Rather than improving performance by increasing MOF coverage or forming dense, continuous MOF coatings, the crystal size and deposition behavior of HKUST-1 were deliberately regulated to achieve a uniform yet non-continuous distribution over the inner and outer surfaces of hollow MnO 2 microtubes. This architecture simultaneously enhances pollutant enrichment, preserves the accessibility of MnO 2 catalytic sites, and maintains autonomous micromotor propulsion, thereby establishing a rational design principle for integrating adsorption, catalytic activity, and self-propulsion in multifunctional MOF-based environmental micromotors. Download: Download high-res image (318KB) Download: Download full-size image