Controllable Assembly of Mo₃₆^VI-Based Polyoxometalate Porous Frameworks with Silver Ions and Lung Cancer Cell-Specific Cytotoxicity

The controllable construction of pure inorganic polyoxometalate (POM)zite materials with well-defined secondary building units (SBUs) is of great challenge. In this work, three distinct POM porous framework compounds 1-3 based on [(Mo36O112)-O-VI(H2O)(16)](8-)({Mo-36}) SBUs with various active growth points and transition-metal Ag linkers, both as countercations and structure directors, were self-assembled from simple salts to ordered porous frameworks (compound 1 is a 3D framework with channels of 20.1 angstrom in diameter, while compound 2 and compound 3 are 2D frameworks with channels of 29.1 and 26.8 angstrom in diameter, respectively, and the channels of compound 3 are formed by the fourfold spiral winding of {Mo-36} SBUs) by controlling the reaction conditions, providing valuable experience for synthetic chemists to obtain more interesting and functional materials. The {Mo-36}-based POM porous framework compounds 1-3 exhibit cell type-specific, dose-dependent, and pH-sensitive anticancer behavior, with the lowest IC50 in A549 lung cancer cells. Further, the monomer precursors AgNO3 and Mo-36 SBU, however, are less cytotoxic to A549 cells than compound Ag-{Mo-36}, suggesting a synergistic action of hybrid materials. Mechanistic insights into the anticancer activity of compounds 1-3 show that they induce mitochondria-mediated apoptosis and necrosis in A549 cells. Thus, {Mo-36}-based POM porous framework materials with silver ions could serve as promising anticancer agents for lung cancer therapy.