U5P8H8(CO6)4 crystallizes in the triclinic P-1 space group. There are three inequivalent U sites. In the first U site, U(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(5), one O(7), one O(9), and two equivalent O(6) atoms. The U(1)-O(1) bond length is 2.57 Å. The U(1)-O(2) bond length is 2.36 Å. The U(1)-O(3) bond length is 2.25 Å. The U(1)-O(5) bond length is 2.27 Å. The U(1)-O(7) bond length is 2.25 Å. The U(1)-O(9) bond length is 2.37 Å. There is one shorter (2.39 Å) and one longer (2.66 Å) U(1)-O(6) bond length. In the second U site, U(2) is bonded in a distorted pentagonal planar geometry to one O(1), one O(10), one O(8), and two equivalent O(4) atoms. The U(2)-O(1) bond length is 2.63 Å. The U(2)-O(10) bond length is 2.27 Å. The U(2)-O(8) bond length is 2.27 Å. There is one shorter (2.43 Å) and one longer (2.49 Å) U(2)-O(4) bond length. In the third U site, U(3) is bonded in a square co-planar geometry to two equivalent O(11) and two equivalent O(12) atoms. Both U(3)-O(11) bond lengths are 2.31 Å. Both U(3)-O(12) bond lengths are 2.30 Å. There are two inequivalent C sites. In the first C site, 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 1.80 Å. Both C(1)-H(1,2) bond lengths are 0.97 Å. In the second C site, C(2) is bonded in a distorted water-like geometry to one P(3), one P(4), one H(3), and one H(4) atom. The C(2)-P(3) bond length is 1.83 Å. The C(2)-P(4) bond length is 1.78 Å. The C(2)-H(3) bond length is 0.97 Å. The C(2)-H(4) bond length is 0.97 Å. There are four inequivalent P sites. In the first P site, P(1) is bonded to one C(1), one O(11), one O(6), and one O(9) atom to form corner-sharing PCO3 tetrahedra. The P(1)-O(11) bond length is 1.50 Å. The P(1)-O(6) bond length is 1.55 Å. The P(1)-O(9) bond length is 1.54 Å. In the second P site, P(2) is bonded to one C(1), one O(1), one O(2), and one O(4) atom to form corner-sharing PCO3 tetrahedra. The P(2)-O(1) bond length is 1.56 Å. The P(2)-O(2) bond length is 1.50 Å. The P(2)-O(4) bond length is 1.55 Å. In the third P site, P(3) is bonded to one C(2), one O(10), one O(7), and one O(8) atom to form distorted corner-sharing PCO3 tetrahedra. The P(3)-O(10) bond length is 1.51 Å. The P(3)-O(7) bond length is 1.52 Å. The P(3)-O(8) bond length is 1.53 Å. In the fourth P site, P(4) is bonded to one C(2), one O(12), one O(3), and one O(5) atom to form corner-sharing PCO3 tetrahedra. The P(4)-O(12) bond length is 1.51 Å. The P(4)-O(3) bond length is 1.53 Å. The P(4)-O(5) bond length is 1.53 Å. There are three inequivalent H sites. In the first H site, H(1,2) is bonded in a single-bond geometry to one C(1) atom. In the second H site, H(3) is bonded in a single-bond geometry to one C(2) atom. In the third H site, H(4) is bonded in a single-bond geometry to one C(2) atom. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one U(1), one U(2), and one P(2) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one U(1) and one P(2) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one U(1) and one P(4) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to two equivalent U(2) and one P(2) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one U(1) and one P(4) atom. In the sixth O site, O(6) is bonded in a 1-coordinate geometry to two equivalent U(1) and one P(1) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one U(1) and one P(3) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one U(2) and one P(3) atom. In the ninth O site, O(9) is bonded in a water-like geometry to one U(1) and one P(1) atom. In the tenth O site, O(10) is bonded in a distorted single-bond geometry to one U(2) and one P(3) atom. In the eleventh O site, O(11) is bonded in a distorted bent 150 degrees geometry to one U(3) and one P(1) atom. In the twelfth O site, O(12) is bonded in a distorted single-bond geometry to one U(3) and one P(4) atom. Linkers: 4 [O]P([O])(=O)CP([O])([O])=O. Metal clusters: 5 [U]. The MOF has largest included sphere 6.12 A, density 2.89 g/cm3, surface area 1500.48 m2/g, accessible volume 0.18 cm3/g