Benzene-1,2-diphosphonic acid (Ppb) was introduced into the uranyl peroxide cluster system, resulting in three Ppb-functionalized uranyl peroxide clusters, (UO2)(20)(O-2)(20)(C6H4P2O6)(10)(40-) (U(20)Ppb(10)), (UO2)(26 )(O-2)(33) (C6H4P2O6)(6)(38-) (U(26)Ppb(6)), and (UO2)(20)(O-2)(24)(C6H4P2O6)(6)(32-) (U(20)Ppb(6)). Dissolution experiments were performed for the potassium salts of U(20)Ppb(10) and U(26)Ppb(6), which revealed the capacity of U(20)Ppb(10 )to dissolve in the organic solvent dimethyl sulfoxide (DMSO). Unlike U(20)Ppb(10), the K salt of U(26)Ppb(6) did not dissolve in DMSO but was more soluble in water, perhaps due to the lower proportion of Ppb ligands in its structure. In this work, U(20)Ppb(10) and U(20)Ppb(6) formed as potassium salts and both adopt the fullerene topology of previously reported U-20. U-20 contains 20 uranyl peroxide units and encapsulates 12 Na cations. It is not possible for unfunctionalized U-20 to incorporate 12 K cations owing to space constraints, as is the case in the new clusters reported here. Transformation of U(21)Ppb(10) in water over time to produce U-24 was observed, possibly owing to its ability to incorporate K cations, which have been associated with the formation of U-24.