NUCLEOLIN and cancer: When these ATP/Mg2+ ion‐responsive NMOFs were loaded with DOX, they demonstrated selective cytotoxicity against MDA‐MB‐231 cancer cells because of the enhanced permeation of the NMOFs into the cells via receptor‐mediated endocytosis (the AS1411 aptamer sequence binds to the nucleolin in cancer cells) and the targeted permeation of the NMOFs into the cells.