Membrane technology is an energy-efficient approach for purification of wastewater. In this work, for the first time, a novel pure zeolite imidazolate framework-300 (ZIF-300) MOF membrane was fabricated and applied for removing heavy metal ions from wastewater. The fine structure of ZIF-300 layer was characterized by positron annihilation spectroscopy technique. Cross-flow and long-term operation test was also carried out to investigate the membrane stability. The obtained ZIF-300 membrane exhibited a high and stable performance with the water permeance of 39.2 L/m(2) h bar and rejection rate of 99.21% for CuSO4. This high separation performance combined the extraordinary stability demonstrated that the as-prepared pure ZIF-300 MOF membrane could be a potential candidate for the water treatment.