Metal-Organic Frameworks as Micromotors with Tunable Engines and Brakes.

Herein, we report that UiO-type (UiO = University of Oslo) metal-organic frameworks (MOFs) can be transformed into self-propelled micromotors by employing several different metal-based propulsion systems. Incorporation of a bipyridine ligand into the UiO-67 lattice transforms the crystallites, upon metalation, into single-site, metal-based catalytic "engines" to power the micromotors with chemical fuel. The "engine performance" (i.e., propulsion) of the single-site powered micromotors has been tuned by the choice of the metal ion utilized. In addition, a chemical "braking" system was achieved by adding chelating agents capable of sequestering the metal ion engines and thereby suppressing the catalytic activity, with different chelators displaying different deceleration capacities. These results demonstrate that MOFs can be powered by various engines and halted by different brakes, resulting in a high degree of motion design and control at the nanoscale.