The present disclosure provides a method for purifying nanostructured material comprising carbon nanotubes, metal impurities and amorphous carbon impurities. The method generally includes oxidizing the unpurified nanostructured material to remove the amorphous carbon and thereby exposing the metal impurities and subsequently contacting the nanostructured material with carbon monoxide to volatilize the metal impurities and thereby substantially remove them from the nanostructured material.