The hydrothermal reaction of phosphonoacetic acid (H2PO3CH2C(O)OH, PAA) with UO3 and Cu(C2H3O2)2 .H2O results in the formation of the crystalline heterobimetallic uranium(VI)/copper(II) phosphonates UO2Cu(PO3CH2CO2)(OH)(H2O)2 ( UCuPAA-1), (UO2) 2Cu(PO3CH2CO2)2(H2O)3 (UCuPAA-2), and [H3O][(UO2) 2Cu2(PO3CH2CO2)3(H2O)2 ( UCuPAA-3). The addition of sodium hydroxide to the aforementioned reactions results in the formation of Na[UO2(PO3CH2CO2)].2H2O (NaUPAA-1). These compounds display 1D (UCuPAA-1), 2D (UCuPAA-2, NaUPAA-1), and 3D (UCuPAA-3) architectures wherein the phosphonate portion of the ligand primarily coordinates the uranium(VI) centers; whereas the carboxylate moiety preferentially, but not exclusively, binds to the copper(II) ions. Fluorescence measurements on all four compounds demonstrate that the presence of copper(II) mostly quenches the emission from the uranyl moieties.

Four heterobimetallic U(vi)/M(ii) (M = Mn, Co, Cd) carboxyphosphonates have been synthesized. M(2)[(UO(2))(6)(PO(3)CH(2)CO(2))(3)O(3)(OH)(H(2)O)(2)]·16H(2)O (M = Mn(ii), Co(ii), and Cd(ii)) adopt cubic three-dimensional network structures with large cavities approximately 16 Å in diameter that are filled with co-crystallized water molecules. [Cd(3)(UO(2))(6)(PO(3)CH(2)CO(2))(6)(H(2)O)(13)]·6H(2)O forms a rhombohedral channel structure with hydrated Cd(ii) within the channels. The cubic compound (Co) displays differential gas absorption with a surface area for CO(2) uptake of 40 m(2) g(-1) at 273 K, and no uptake of N(2) at 77 K.

Five heterobimetallic U(VI)/Co(II) carboxyphosphonates have been synthesized under mild hydrothermal conditions by reacting UO 3 , Co(CH 3 CO 2) 2 3 4H 2 O, and triethyl phosphonoacetate. These compounds, Co(H 2 O) 4 [(UO 2) 2 (PO 3-CH 2 CO 2) 2 (H 2 O) 2 ] (CoUPAA-1), [Co(H 2 O) 6 ][UO 2 (PO 3 CH 2 CO 2)] 2 3 8H 2 O (CoUPAA-2), Co(H 2 O) 4 [UO 2 (PO 3 CH 2 CO 2)] 2 3 4H 2 O (CoUPAA-3), Co(H 2 O) 4 [(UO 2) 6 (PO 3 CH 2 CO 2) 2 O 2 (OH) 3 (H 2 O) 3 ] 2 3 3H 2 O (CoUPAA-4), and Co 2 [(UO 2) 6 (PO 3 CH 2-CO 2) 3 O 3 (OH)(H 2 O) 2 ] 3 16H 2 O (CoUPAA-5), range from two-to three-dimensional structures. CoUPAA-1 to CoUPAA-3 all possess uranyl carboxyphosphonate layers that are separated by the Co(II) cation with varying degrees of hydration. CoUPAA-4 contains both UO 7 pentagonal bipyramids and UO 8 hexagonal bipyramids within the uranyl carboxyphosphonate plane. Unlike the first four low-symmetry compounds, CoUPAA-5 is a cubic, three-dimensional network with large cavities approximately 16 Å in diameter that are filled with cocrystallized water molecules. Differential gas absorption measurements performed on CoUPAA-5 displayed a surface area uptake for CO 2 of 40 m 2 g-1 at 273 K, and no uptake for N 2 at 77 K.

The hydrothermal reactions of KCl, RbCl, CsOH, and CsCl with phosphonoacetic acid and uranium trioxide at 180 degrees C for three to five days results in the formation of five different crystalline uranyl carboxyphosphonates, K[(UO(2))(2)(PO(3)CH(2)CO(2))(PO(3)CH(2)CO(2)H)(H(2)O)] x H(2)O, Rb[(UO(2))(2)(PO(3)CH(2)CO(2))(PO(3)CH(2)CO(2)H)(H(2)O)] x H(2)O, Cs[(UO(2))(2)(PO(3)CH(2)CO(2))(PO(3)CH(2)CO(2)H)(H(2)O)] x H(2)O, Cs[(UO(2))(PO(3)CH(2)CO(2))], and Cs(3)[(UO(2))(4)(PO(3)CH(2)O(2))(2)(PO(3)CH(2)CO(2)H(0.5))(2)] x nH(2)O, respectively. In all compounds, the UO(2)(2+) moieties are bound by phosphonate and carboxylate forming pentagonal bipyramidal environments around the uranium centers. At low pH, some of the carboxylate portions of the phosphonoacetate are protonated. The addition of hydroxide removes these protons, and a different structure is adopted. In contrast to all other uranyl carboxyphosphonates, Cs(3)[(UO(2))(4)(PO(3)CH(2)O(2))(2)(PO(3)CH(2)CO(2)H(0.5))(2)] x nH(2)O adopts a three-dimensional network structure with large channels along the c axis that house the Cs(+) cations.

Five heterobimetallic U(VI)/M(II) (M = Mn, Fe) carboxyphosphonates have been synthesized under mild hydrothermal conditions by reacting UO3, triethyl phosphonoacetate, with either Mn(II) or Fe(II) acetate. The manganese reactions yield Mn2[(UO2)6(PO3CH2CO2)3O3(OH)(H2O)2]·16H2O (MnUPAA-1) and [Mn(H2O)6][Mn(H2O)5Mn2(UO2)5(PO3CH2CO2)6(H2O)]·5.75H2O (MnUPAA-2). The addition of boric acid, which lowers the crystallization temperature, allows for the production of a third product, [Mn(H2O)4]2(UO2)3(PO3CH2CO2)2O2 (MnUPAA-3). The iron-containing reactions yield [Fe(H2O)6][UO2(PO3CH2CO2)]2·8H2O (FeUPAA-1) and [Fe(H2O)6][UO2(PO3CH2CO2)H2O]2·4H2O (FeUPAA-2). Four of these five compounds crystallize in low-symmetry space groups; whereas MnUPAA-1 crystallizes in the cubic space group Im3̅ and possesses a remarkably complex open-framework structure containing both UO7 pentagonal bipyramids and UO8 hexagonal bipyramids. MnUPAA-3 adopts a one-dimensional uranium oxide topology that contains both UO6 tetragonal bipyramids and UO7 pentagonal bipyramids. The remaining three compounds solely contain UO7 pentagonal bipyramids.