BaH6(C2O5)2 crystallizes in the monoclinic C2/c space group. Ba(1) is bonded to two equivalent O(2), two equivalent O(3), two equivalent O(4), two equivalent O(5), and four equivalent O(1) atoms to form edge-sharing BaO12 cuboctahedra. Both Ba(1)-O(2) bond lengths are 3.00 Å. Both Ba(1)-O(3) bond lengths are 2.84 Å. Both Ba(1)-O(4) bond lengths are 2.86 Å. Both Ba(1)-O(5) bond lengths are 2.93 Å. There are two shorter (2.99 Å) and two longer (3.22 Å) Ba(1)-O(1) bond lengths. There are two inequivalent C sites. In the first C site, C(2) is bonded in a distorted bent 120 degrees geometry to one O(1) and one O(5) atom. The C(2)-O(1) bond length is 1.23 Å. The C(2)-O(5) bond length is 1.31 Å. In the second C site, C(1) is bonded in a distorted bent 120 degrees geometry to one O(2) and one O(3) atom. The C(1)-O(2) bond length is 1.25 Å. The C(1)-O(3) bond length is 1.28 Å. There are three inequivalent H sites. In the first H site, H(1) is bonded in a linear geometry to one O(3) and one O(5) atom. The H(1)-O(3) bond length is 1.35 Å. The H(1)-O(5) bond length is 1.11 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(4) atom. The H(2)-O(4) bond length is 0.99 Å. In the third H site, H(3) is bonded in a single-bond geometry to one O(4) atom. The H(3)-O(4) bond length is 0.98 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to two equivalent Ba(1) and one C(2) atom. In the second O site, O(5) is bonded in a distorted water-like geometry to one Ba(1), one C(2), and one H(1) atom. In the third O site, O(2) is bonded in a single-bond geometry to one Ba(1) and one C(1) atom. In the fourth O site, O(3) is bonded in a bent 120 degrees geometry to one Ba(1), one C(1), and one H(1) atom. In the fifth O site, O(4) is bonded in a water-like geometry to one Ba(1), one H(2), and one H(3) atom. Linkers: 1 O=C(O)C(=O)O ,2 [O]C(=O)C(=O)O ,1 [O]C(=O)C([O])=O. Metal clusters: 2 [Ba]. The MOF has largest included sphere 1.55 A, density 2.64 g/cm3, surface area 2300.20 m2/g, accessible volume 0.05 cm3/g