CdC4H4O6 crystallizes in the trigonal R-3 space group. Cd(1) is bonded in an octahedral geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. Both Cd(1)-O(1) bond lengths are 2.39 Å. Both Cd(1)-O(2) bond lengths are 2.36 Å. Both Cd(1)-O(3) bond lengths are 2.23 Å. There are two inequivalent C sites. In the first C site, C(1) is bonded in a single-bond geometry to one O(1) atom. The C(1)-O(1) bond length is 1.26 Å. In the second 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. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(1) and one O(3) atom. The H(1)-O(1) bond length is 1.73 Å. The H(1)-O(3) bond length is 1.00 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(2) and one O(3) atom. The H(2)-O(2) bond length is 1.72 Å. The H(2)-O(3) bond length is 1.00 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Cd(1), one C(1), and one H(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Cd(1), one C(2), and one H(2) atom. In the third O site, O(3) is bonded in a distorted water-like geometry to one Cd(1), one H(1), and one H(2) atom. Linkers: 3 O=C1C(=O)C(=O)C1=O. Metal clusters: 3 [Cd]. RCSR code: nbo. The MOF has largest included sphere 5.24 A, density 2.09 g/cm3, surface area 3141.58 m2/g, accessible volume 0.18 cm3/g