BaH4(C2O3)2 crystallizes in the orthorhombic P2_12_12_1 space group. Ba(1) is bonded in a 9-coordinate geometry to one O(2), one O(3), one O(6), two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms. The Ba(1)-O(2) bond length is 2.85 Å. The Ba(1)-O(3) bond length is 2.77 Å. The Ba(1)-O(6) bond length is 2.82 Å. There is one shorter (2.81 Å) and one longer (2.86 Å) Ba(1)-O(1) bond length. There is one shorter (2.83 Å) and one longer (2.88 Å) Ba(1)-O(4) bond length. There is one shorter (2.79 Å) and one longer (2.90 Å) Ba(1)-O(5) bond length. There are four inequivalent C sites. In the first C site, C(4) is bonded in a distorted bent 120 degrees geometry to one O(5) and one O(6) atom. The C(4)-O(5) bond length is 1.27 Å. The C(4)-O(6) bond length is 1.27 Å. In the second 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. In the third C site, C(2) is bonded in a distorted water-like geometry to one H(3) and one O(3) atom. The C(2)-H(3) bond length is 1.10 Å. The C(2)-O(3) bond length is 1.42 Å. In the fourth C site, C(3) is bonded in a distorted water-like geometry to one H(4) and one O(4) atom. The C(3)-H(4) bond length is 1.10 Å. The C(3)-O(4) bond length is 1.43 Å. There are four inequivalent H sites. In the first H site, H(1) is bonded in a distorted single-bond geometry to one O(2) and one O(3) atom. The H(1)-O(2) bond length is 1.64 Å. The H(1)-O(3) bond length is 1.01 Å. In the second H site, H(2) is bonded in a distorted linear geometry to one O(4) and one O(6) atom. The H(2)-O(4) bond length is 1.02 Å. The H(2)-O(6) bond length is 1.61 Å. In the third H site, H(3) is bonded in a single-bond geometry to one C(2) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one C(3) atom. There are six 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(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ba(1), one C(1), and one H(1) atom. In the third O site, O(3) is bonded in a distorted water-like geometry to one Ba(1), one C(2), and one H(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one C(3), and one H(2) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one C(4) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Ba(1), one C(4), and one H(2) atom. Linkers: 4 [O]C(=O)[C@H](O)[C@@H](O)C([O])=O. Metal clusters: 4 [Ba]. The MOF has largest included sphere 1.84 A, density 3.00 g/cm3, surface area 1861.92 m2/g, accessible volume 0.03 cm3/g