BaH6(C2O3)2 crystallizes in the orthorhombic Pna2_1 space group. Ba(1) is bonded in a 8-coordinate geometry to one O(1), one O(3), one O(5), one O(6), two equivalent O(2), and two equivalent O(4) atoms. The Ba(1)-O(1) bond length is 2.85 Å. The Ba(1)-O(3) bond length is 2.77 Å. The Ba(1)-O(5) bond length is 2.87 Å. The Ba(1)-O(6) bond length is 2.76 Å. There is one shorter (2.75 Å) and one longer (2.80 Å) Ba(1)-O(2) bond length. There is one shorter (2.75 Å) and one longer (2.79 Å) Ba(1)-O(4) bond length. There are four inequivalent C sites. In the first C site, C(2) is bonded in a distorted trigonal non-coplanar geometry to one H(1,4); one H(2,3); and one O(3) atom. The C(2)-H(1,4) bond length is 1.10 Å. The C(2)-H(2,3) bond length is 1.10 Å. The C(2)-O(3) bond length is 1.43 Å. In the second C site, C(3) is bonded in a distorted trigonal non-coplanar geometry to one H(1,4); one H(2,3); and one O(3) atom. The C(3)-H(1,4) bond length is 1.10 Å. The C(3)-H(2,3) bond length is 1.10 Å. The C(3)-O(3) bond length is 1.43 Å. In the third C site, C(4) is bonded in a distorted bent 120 degrees geometry to one O(4) and one O(5) atom. The C(4)-O(4) bond length is 1.28 Å. The C(4)-O(5) bond length is 1.27 Å. In the fourth C site, C(1) is bonded in a distorted bent 120 degrees geometry to one O(1) and one O(2) atom. The C(1)-O(1) bond length is 1.26 Å. The C(1)-O(2) bond length is 1.28 Å. There are four inequivalent H sites. In the first H site, H(1,4) is bonded in a single-bond geometry to one C(2) atom. In the second H site, H(2,3) is bonded in a single-bond geometry to one C(2) atom. In the third H site, H(5) is bonded in a single-bond geometry to one O(6) atom. The H(5)-O(6) bond length is 0.99 Å. In the fourth H site, H(6) is bonded in a single-bond geometry to one O(6) atom. The H(6)-O(6) bond length is 0.99 Å. There are six inequivalent O sites. In the first O site, O(6) is bonded in a water-like geometry to one Ba(1), one H(5), and one H(6) atom. In the second O site, O(1) is bonded in a single-bond geometry to one Ba(1) and one C(1) atom. In the third O site, O(5) is bonded in a single-bond geometry to one Ba(1) and one C(4) atom. In the fourth O site, O(2) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one C(1) atom. In the fifth O site, O(3) is bonded in a distorted water-like geometry to one Ba(1), one C(2), and one C(3) atom. In the sixth O site, O(4) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one C(4) atom. Linkers: 4 [O]C(=O)COCC([O])=O. Metal clusters: 4 [Ba]. The MOF has largest included sphere 1.50 A, density 2.66 g/cm3, surface area 2528.25 m2/g, accessible volume 0.04 cm3/g