UCP2H2O6 crystallizes in the trigonal P3_121 space group. U(1) is bonded in a pentagonal planar geometry to one O(1), one O(2), one O(3), one O(4), and one O(5) atom. The U(1)-O(1) bond length is 2.39 Å. The U(1)-O(2) bond length is 2.37 Å. The U(1)-O(3) bond length is 2.36 Å. The U(1)-O(4) bond length is 2.37 Å. The U(1)-O(5) bond length is 2.33 Å. C(1) is bonded in a distorted tetrahedral geometry to one P(1); one P(2); and two equivalent H(1,2) atoms. The C(1)-P(1) bond length is 1.81 Å. The C(1)-P(2) bond length is 1.78 Å. Both C(1)-H(1,2) bond lengths are 0.99 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one C(1), one O(4), one O(5), and one O(6) atom to form corner-sharing PCO3 tetrahedra. The P(1)-O(4) bond length is 1.53 Å. The P(1)-O(5) bond length is 1.52 Å. The P(1)-O(6) bond length is 1.51 Å. In the second P site, P(2) is bonded to one C(1), one O(1), one O(2), and one O(3) atom to form corner-sharing PCO3 tetrahedra. The P(2)-O(1) bond length is 1.53 Å. The P(2)-O(2) bond length is 1.53 Å. The P(2)-O(3) bond length is 1.51 Å. H(1,2) is bonded in a single-bond geometry to one C(1) atom. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one U(1) and one P(2) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one U(1) and one P(2) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one U(1) and one P(2) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one U(1) and one P(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one U(1) and one P(1) atom. In the sixth O site, O(6) is bonded in a single-bond geometry to one P(1) atom. Linkers: 6 [O]P([O])(=O)CP([O])([O])=O. Metal clusters: 6 [U]. The MOF has largest included sphere 7.05 A, density 1.85 g/cm3, surface area 1847.26 m2/g, accessible volume 0.30 cm3/g