Self-Propelled Nanomotor Based on Hierarchical Metal-Organic Frameworks Composites for the Removal of Heavy Metal Ions

The outstanding removal performances of heavy metal ions are inseparable from a) the sufficient contact probability between heavy metal ions and adsorbent, b) convenient diffusion/accessibility of heavy metal ions on the surface and inside adsorbent, and c) abundant binding sites for heavy metal ions on adsorbent. Herein, we designed an efficient adsorbent of MnFe2O4@MIL-53@UiO-66@MnO2 for Pb(II) and Cd(II) removal based on merging the self-propelled nanomotor, hierarchical structure and composite metal-organic frameworks (MOFs) to meet the above three requirements at the same time. The sufficient contact probability between Pb(II)/Cd(II) and MnFe2O4@MIL-53@UiO-66@MnO2 was achieved via self-propelled movement of the nanomotor induced by the catalytic decomposition of H2O2 by MnO2. The convenient diffusion/accessibility of Pb(II)/Cd(II) on the surface and inside MnFe2O4@MIL-53@UiO-66@MnO2 was realized by a hierarchical structured adsorbent constructed from different sophisticated complexing materials (MnFe2O4, MIL-53, UiO-66 and MnO2) with different pore sizes. Abundant binding sites (-COOH) from organic linker of MIL-53 and UiO-66 composite were provided for Pb(II)/Cd(II) ions to bind with the adsorbent. Besides, the complex of MnFe2O4 and MIL-53 endows the adsorbent with easy-recyclable property under an extra magnet. The nanomotor owns gratifying removal performances for Pb(II) and Cd(II) with excellent adsorption capacities and rapid removal rates