Hydrothermal reactions of aluminum(III) nitrate or iron(III) nitrate with N,N-dimethylaminomethane-1,1-diphosphonic acid (H4L) and sodium hydroxide lead to two novel isostructural octanuclear metal phosphonate cages encapsulating two Na-I ions, namely, [Al8Na2(HL)(2)(H2L)(10)(H2O)(6)]center dot 20H(2)O (1) and [Fe8Na2(HL)(2)(H2L)(10)-(H2O)(6)]center dot 22H(2)O (2). The molecular structure of 1 can be viewed as a three-in-one cluster, in which a central zeolite D6R SBU lookalike aluminophosphonate cage is capped by two symmetry-related aluminophosphonate tetrahedral Gages above and below and such a tetrahedral cage, being composed of four zeolite S6R SBU lookalike aluminophosphonate rings, further hexadentately traps one Na+ ion in its cavity.