CdH4(C2O)4 crystallizes in the monoclinic C2/c space group. There are two inequivalent Cd sites. In the first Cd site, Cd(1) is bonded to one O(2), one O(3), one O(4), one O(6), and two equivalent O(1) atoms to form distorted edge-sharing CdO6 pentagonal pyramids. The Cd(1)-O(2) bond length is 2.44 Å. The Cd(1)-O(3) bond length is 2.30 Å. The Cd(1)-O(4) bond length is 2.50 Å. The Cd(1)-O(6) bond length is 2.24 Å. There is one shorter (2.35 Å) and one longer (2.38 Å) Cd(1)-O(1) bond length. In the second Cd site, Cd(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms to form edge-sharing CdO6 octahedra. Both Cd(2)-O(2) bond lengths are 2.38 Å. Both Cd(2)-O(4) bond lengths are 2.28 Å. Both Cd(2)-O(5) bond lengths are 2.19 Å. There are twelve inequivalent C sites. In the first C site, C(1) is bonded in a bent 120 degrees geometry to one C(2), one O(1), and one O(2) atom. The C(1)-C(2) bond length is 1.50 Å. The C(1)-O(1) bond length is 1.26 Å. The C(1)-O(2) bond length is 1.26 Å. In the second C site, C(2) is bonded in a trigonal planar geometry to one C(1), one C(10), and one C(6) atom. The C(2)-C(10) bond length is 1.39 Å. The C(2)-C(6) bond length is 1.38 Å. In the third C site, C(3) is bonded in a distorted trigonal planar geometry to one C(6), one C(8), and one H(1) atom. The C(3)-C(6) bond length is 1.39 Å. The C(3)-C(8) bond length is 1.38 Å. The C(3)-H(1) bond length is 1.14 Å. In the fourth C site, C(4) is bonded in a distorted bent 120 degrees geometry to one C(5), one O(4), and one O(6) atom. The C(4)-C(5) bond length is 1.50 Å. The C(4)-O(4) bond length is 1.25 Å. The C(4)-O(6) bond length is 1.24 Å. In the fifth C site, C(5) is bonded in a trigonal planar geometry to one C(12), one C(4), and one C(9) atom. The C(5)-C(12) bond length is 1.39 Å. The C(5)-C(9) bond length is 1.39 Å. In the sixth C site, C(6) is bonded in a distorted trigonal planar geometry to one C(2), one C(3), and one H(2) atom. The C(6)-H(2) bond length is 1.14 Å. In the seventh C site, C(7) is bonded in a distorted bent 120 degrees geometry to one C(8), one O(3), and one O(5) atom. The C(7)-C(8) bond length is 1.53 Å. The C(7)-O(3) bond length is 1.25 Å. The C(7)-O(5) bond length is 1.27 Å. In the eighth C site, C(8) is bonded in a trigonal planar geometry to one C(11), one C(3), and one C(7) atom. The C(8)-C(11) bond length is 1.39 Å. In the ninth C site, C(9) is bonded in a distorted trigonal planar geometry to one C(12), one C(5), and one H(3) atom. The C(9)-C(12) bond length is 1.39 Å. The C(9)-H(3) bond length is 1.14 Å. In the tenth C site, C(10) is bonded in a distorted single-bond geometry to one C(11), one C(2), and one H(4) atom. The C(10)-C(11) bond length is 1.38 Å. The C(10)-H(4) bond length is 1.14 Å. In the eleventh C site, C(11) is bonded in a distorted trigonal planar geometry to one C(10), one C(8), and one H(5) atom. The C(11)-H(5) bond length is 1.14 Å. In the twelfth C site, C(12) is bonded in a distorted trigonal planar geometry to one C(5), one C(9), and one H(6) atom. The C(12)-H(6) bond length is 1.14 Å. There are six inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one C(3) atom. In the second H site, H(2) is bonded in a single-bond geometry to one C(6) atom. In the third H site, H(3) is bonded in a single-bond geometry to one C(9) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one C(10) atom. In the fifth H site, H(5) is bonded in a single-bond geometry to one C(11) atom. In the sixth H site, H(6) is bonded in a single-bond geometry to one C(12) atom. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to two equivalent Cd(1) and one C(1) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Cd(1), one Cd(2), and one C(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Cd(1) and one C(7) atom. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Cd(1), one Cd(2), and one C(4) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Cd(2) and one C(7) atom. In the sixth O site, O(6) is bonded in a water-like geometry to one Cd(1) and one C(4) atom. Linkers: 6 [O]C(=O)c1ccc(C([O])=O)cc1. Metal clusters: 6 [Cd]. The MOF has largest included sphere 6.68 A, density 1.38 g/cm3, surface area 3225.30 m2/g, accessible volume 0.38 cm3/g