CdC4H4O6 crystallizes in the monoclinic P2_1/c space group. Cd(1) is bonded to one O(1), one O(3), one O(4), one O(5), and two equivalent O(6) atoms to form corner-sharing CdO6 octahedra. The corner-sharing octahedral tilt angles are 55°. The Cd(1)-O(1) bond length is 2.26 Å. The Cd(1)-O(3) bond length is 2.24 Å. The Cd(1)-O(4) bond length is 2.55 Å. The Cd(1)-O(5) bond length is 2.26 Å. There is one shorter (2.36 Å) and one longer (2.44 Å) Cd(1)-O(6) bond length. There are four inequivalent C sites. In the first C site, C(4) is bonded in a distorted single-bond geometry to one O(4) atom. The C(4)-O(4) bond length is 1.28 Å. In the second C site, C(1) is bonded in a distorted single-bond geometry to one O(1) atom. The C(1)-O(1) bond length is 1.26 Å. In the third C site, C(2) is bonded in a single-bond geometry to one O(2) atom. The C(2)-O(2) bond length is 1.26 Å. In the fourth C site, C(3) is bonded in a distorted single-bond geometry to one O(3) atom. The C(3)-O(3) bond length is 1.26 Å. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(4) and one O(5) atom. The H(1)-O(4) bond length is 1.73 Å. The H(1)-O(5) bond length is 0.99 Å. In the second H site, H(2) is bonded in a distorted single-bond geometry to one O(2) and one O(5) atom. The H(2)-O(2) bond length is 1.68 Å. The H(2)-O(5) bond length is 1.00 Å. In the third H site, H(3) is bonded in a distorted linear geometry to one O(4) and one O(6) atom. The H(3)-O(4) bond length is 1.64 Å. The H(3)-O(6) bond length is 1.01 Å. In the fourth H site, H(4) is bonded in a linear geometry to one O(2) and one O(6) atom. The H(4)-O(2) bond length is 1.57 Å. The H(4)-O(6) bond length is 1.02 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Cd(1) and one C(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one C(2), one H(2), and one H(4) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Cd(1) and one C(3) atom. In the fourth O site, O(4) is bonded in a distorted tetrahedral geometry to one Cd(1), one C(4), one H(1), and one H(3) atom. In the fifth O site, O(5) is bonded in a distorted water-like geometry to one Cd(1), one H(1), and one H(2) atom. In the sixth O site, O(6) is bonded in a distorted water-like geometry to two equivalent Cd(1), one H(3), and one H(4) atom. Linkers: 4 O=C1C(=O)C(=O)C1=O ,4 O. Metal clusters: 4 [Cd]. The MOF has largest included sphere 1.43 A, density 2.83 g/cm3, surface area 2494.98 m2/g, accessible volume 0.07 cm3/g