U3P4H8(C2O7)2 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent U sites. In the first U site, U(1) is bonded in a 4-coordinate geometry to one O(1), one O(11), one O(12), and one O(2) atom. The U(1)-O(1) bond length is 2.30 Å. The U(1)-O(11) bond length is 2.38 Å. The U(1)-O(12) bond length is 2.41 Å. The U(1)-O(2) bond length is 2.34 Å. In the second U site, U(2) is bonded in a 4-coordinate geometry to one O(13), one O(3), one O(4), and one O(5) atom. The U(2)-O(13) bond length is 2.37 Å. The U(2)-O(3) bond length is 2.40 Å. The U(2)-O(4) bond length is 2.40 Å. The U(2)-O(5) bond length is 2.35 Å. In the third U site, U(3) is bonded in a 3-coordinate geometry to one O(6), one O(7), and one O(8) atom. The U(3)-O(6) bond length is 2.29 Å. The U(3)-O(7) bond length is 2.40 Å. The U(3)-O(8) bond length is 2.36 Å. There are four inequivalent C sites. In the first C site, C(1) is bonded in a distorted tetrahedral geometry to one C(2), one P(1), one P(2), and one O(14) atom. The C(1)-C(2) bond length is 1.58 Å. The C(1)-P(1) bond length is 1.83 Å. The C(1)-P(2) bond length is 1.82 Å. The C(1)-O(14) bond length is 1.44 Å. In the second C site, C(2) is bonded in a trigonal non-coplanar geometry to one C(1) and three equivalent H(1,2,3) atoms. All C(2)-H(1,2,3) bond lengths are 0.96 Å. In the third C site, C(3) is bonded in a distorted tetrahedral geometry to one C(4), one P(3), one P(4), and one O(10) atom. The C(3)-C(4) bond length is 1.57 Å. The C(3)-P(3) bond length is 1.82 Å. The C(3)-P(4) bond length is 1.82 Å. The C(3)-O(10) bond length is 1.44 Å. In the fourth C site, C(4) is bonded in a trigonal non-coplanar geometry to one C(3), one H(4), one H(5), and one H(6) atom. The C(4)-H(4) bond length is 0.96 Å. The C(4)-H(5) bond length is 0.96 Å. The C(4)-H(6) bond length is 0.96 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(13), and one O(8) atom to form corner-sharing PCO3 tetrahedra. The P(1)-O(11) bond length is 1.53 Å. The P(1)-O(13) bond length is 1.51 Å. The P(1)-O(8) bond length is 1.50 Å. In the second P site, P(2) is bonded to one C(1), one O(12), one O(5), and one O(9) atom to form corner-sharing PCO3 tetrahedra. The P(2)-O(12) bond length is 1.53 Å. The P(2)-O(5) bond length is 1.51 Å. The P(2)-O(9) bond length is 1.56 Å. In the third P site, P(3) is bonded to one C(3), one O(1), one O(4), and one O(6) atom to form corner-sharing PCO3 tetrahedra. The P(3)-O(1) bond length is 1.52 Å. The P(3)-O(4) bond length is 1.53 Å. The P(3)-O(6) bond length is 1.51 Å. In the fourth P site, P(4) is bonded to one C(3), one O(2), one O(3), and one O(7) atom to form corner-sharing PCO3 tetrahedra. The P(4)-O(2) bond length is 1.51 Å. The P(4)-O(3) bond length is 1.53 Å. The P(4)-O(7) bond length is 1.54 Å. There are six inequivalent H sites. In the first H site, H(1,2,3) is bonded in a single-bond geometry to one C(2) atom. In the second H site, H(4) is bonded in a single-bond geometry to one C(4) atom. In the third H site, H(5) is bonded in a single-bond geometry to one C(4) atom. In the fourth H site, H(6) is bonded in a single-bond geometry to one C(4) atom. In the fifth H site, H(7) is bonded in a single-bond geometry to one O(10) atom. The H(7)-O(10) bond length is 0.82 Å. In the sixth H site, H(8) is bonded in a single-bond geometry to one O(14) atom. The H(8)-O(14) bond length is 0.82 Å. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one U(1) and one P(3) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one U(1) and one P(4) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one U(2) and one P(4) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one U(2) and one P(3) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one U(2) and one P(2) atom. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one U(3) and one P(3) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one U(3) and one P(4) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one U(3) and one P(1) atom. In the ninth O site, O(9) is bonded in a single-bond geometry to one P(2) atom. In the tenth O site, O(10) is bonded in a water-like geometry to one C(3) and one H(7) atom. In the eleventh O site, O(11) is bonded in a distorted bent 150 degrees geometry to one U(1) and one P(1) atom. In the twelfth O site, O(12) is bonded in a distorted single-bond geometry to one U(1) and one P(2) atom. In the thirteenth O site, O(13) is bonded in a distorted bent 150 degrees geometry to one U(2) and one P(1) atom. In the fourteenth O site, O(14) is bonded in a water-like geometry to one C(1) and one H(8) atom. Linkers: 8 CC(O)(P([O])([O])=O)P([O])([O])=O. Metal clusters: 12 [U]. The MOF has largest included sphere 6.03 A, density 2.30 g/cm3, surface area 1827.18 m2/g, accessible volume 0.23 cm3/g