Cube-octameric polyhedral silsesquioxanes (R8Si8O12) react with strong acids (HX) to produce R8Si8O11X2 frameworks resulting from selective cleavage of one Si-O-Si linkage; subsequent hydrolysis affords R8Si8O11(OH)(2) frameworks derived from the net hydrolysis of one Si-O-Si linkage in R8Si8O12; these results demonstrate for the first time that readily available R8Si8O12 frameworks can be used as precursors to incompletely condensed Si/O frameworks and have important implications for the manufacture of hybrid inorganic-organic materials based on discrete polyhedral clusters of silicon and oxygen.