CuH3(C2O)4 crystallizes in the trigonal R-3m space group. Cu(1) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(2) atoms. Both Cu(1)-O(1) bond lengths are 1.94 Å. Both Cu(1)-O(2) bond lengths are 1.95 Å. There are five inequivalent C sites. In the first C site, C(1) is bonded in a bent 120 degrees geometry to one C(3), one O(1), and one O(2) atom. The C(1)-C(3) bond length is 1.49 Å. The C(1)-O(1) bond length is 1.25 Å. The C(1)-O(2) bond length is 1.26 Å. In the second C site, C(2) is bonded in a distorted single-bond geometry to one C(3), one C(4), and one H(1) atom. The C(2)-C(3) bond length is 1.38 Å. The C(2)-C(4) bond length is 1.39 Å. The C(2)-H(1) bond length is 0.95 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(5) atom. The C(3)-C(5) bond length is 1.39 Å. In the fourth C site, C(4) is bonded in a trigonal planar geometry to one C(4) and two equivalent C(2) atoms. The C(4)-C(4) bond length is 1.52 Å. In the fifth C site, C(5) is bonded in a distorted single-bond geometry to two equivalent C(3) and one H(2) atom. The C(5)-H(2) bond length is 0.95 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one C(2) atom. In the second H site, H(2) is bonded in a single-bond geometry to one C(5) atom. There are two 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 bent 120 degrees geometry to one Cu(1) and one C(1) atom. Linkers: 3 [O]C(=O)c1cc(C([O])=O)cc(-c2cc(C([O])=O)cc(C([O])=O)c2)c1. Metal clusters: 3 [C]1O[Cu]234O[C]O[Cu]2(O1)(O[C]O3)O[C]O4. RCSR code: nbo. The MOF has largest included sphere 10.05 A, density 0.93 g/cm3, surface area 3340.75 m2/g, accessible volume 0.80 cm3/g