We describe Janus metal organic framework crystals that are propelled by bubble ejection. The Janus crystals are prepared by selective epitaxial growth of ZIF-67 on ZIF-8. The Janus crystals catalyse the decomposition of H2O2 into H2O and O2 on the ZIF-67 surface but not on the zinc containing ZIF-8 surface, resulting in propulsion of the Janus crystals.
