CuC4O3 crystallizes in the trigonal R-3 space group. Cu(1) is bonded to one O(2), two equivalent O(1), and two equivalent O(3) atoms to form distorted edge-sharing CuO5 trigonal bipyramids. The Cu(1)-O(2) bond length is 1.87 Å. There is one shorter (1.93 Å) and one longer (2.52 Å) Cu(1)-O(1) bond length. There is one shorter (1.91 Å) and one longer (2.06 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 bent 120 degrees geometry to one C(2), one O(1), and one O(2) atom. The C(1)-C(2) bond length is 1.53 Å. The C(1)-O(1) bond length is 1.24 Å. The C(1)-O(2) bond length is 1.27 Å. In the second C site, C(2) is bonded in a trigonal planar geometry to one C(1), one C(3), and one C(4) atom. The C(2)-C(3) bond length is 1.41 Å. The C(2)-C(4) bond length is 1.40 Å. In the third C site, C(3) is bonded in a distorted single-bond geometry to one C(2), one C(4), and one O(3) atom. The C(3)-C(4) bond length is 1.31 Å. The C(3)-O(3) bond length is 1.39 Å. In the fourth C site, C(4) is bonded in a bent 120 degrees geometry to one C(2) and one C(3) atom. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Cu(1) and one C(1) atom. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one 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(3) atom. Linkers: 9 [O]C(=O)c1[c]c([O])c(C([O])=O)[c]c1[O]. Metal clusters: 18 [Cu]. The MOF has largest included sphere 11.31 A, density 1.31 g/cm3, surface area 2430.17 m2/g, accessible volume 0.54 cm3/g