CuC4HO3 crystallizes in the trigonal R-3 space group. Cu(1) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(2), and two equivalent O(3) atoms. The Cu(1)-O(1) bond length is 1.92 Å. There is one shorter (1.93 Å) and one longer (2.43 Å) Cu(1)-O(2) bond length. There is one shorter (1.90 Å) and one longer (1.96 Å) Cu(1)-O(3) bond length. There are four inequivalent C sites. In the first C site, C(1) is bonded in a distorted water-like geometry to one C(3), one O(1), and one O(2) atom. The C(1)-C(3) bond length is 1.47 Å. The C(1)-O(1) bond length is 1.31 Å. The C(1)-O(2) bond length is 1.29 Å. In the second C site, C(2) is bonded in a distorted trigonal planar geometry to one C(3), one C(4), and one H(1) atom. The C(2)-C(3) bond length is 1.40 Å. The C(2)-C(4) bond length is 1.41 Å. The C(2)-H(1) bond length is 1.01 Å. In the third C site, C(3) is bonded in a trigonal planar geometry to one C(1), one C(2), and one C(4) atom. The C(3)-C(4) bond length is 1.43 Å. In the fourth C site, C(4) is bonded in a distorted single-bond geometry to one C(2), one C(3), and one O(3) atom. The C(4)-O(3) bond length is 1.40 Å. H(1) is bonded in a single-bond geometry to one C(2) atom. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Cu(1) and one C(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to two equivalent Cu(1) and one C(1) atom. In the third O site, O(3) is bonded in a trigonal non-coplanar geometry to two equivalent Cu(1) and one C(4) atom. Linkers: 9 [O]C(=O)c1cc([O])c(C([O])=O)cc1[O]. Metal clusters: 18 [Cu]. The MOF has largest included sphere 11.29 A, density 1.32 g/cm3, surface area 2414.75 m2/g, accessible volume 0.53 cm3/g