BaH4(C4O3)2 crystallizes in the triclinic P-1 space group. Ba(1) is bonded in a 10-coordinate geometry to one H(4), one O(4), one O(5), one O(6), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. The Ba(1)-H(4) bond length is 3.06 Å. The Ba(1)-O(4) bond length is 2.88 Å. The Ba(1)-O(5) bond length is 2.92 Å. The Ba(1)-O(6) bond length is 2.86 Å. Both Ba(1)-O(1) bond lengths are 2.91 Å. There is one shorter (2.87 Å) and one longer (3.08 Å) Ba(1)-O(2) bond length. There is one shorter (2.80 Å) and one longer (2.88 Å) Ba(1)-O(3) bond length. There are eight 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 1.49 Å. The C(1)-O(1) bond length is 1.27 Å. The C(1)-O(2) bond length is 1.29 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(7) atom. The C(2)-C(3) bond length is 1.40 Å. The C(2)-C(7) bond length is 1.41 Å. In the third C site, C(3) is bonded in a distorted single-bond geometry to one C(2) and one H(3) atom. The C(3)-H(3) bond length is 1.09 Å. In the fourth C site, C(4) is bonded in a distorted single-bond geometry to one C(5) and one O(5) atom. The C(4)-C(5) bond length is 1.42 Å. The C(4)-O(5) bond length is 1.37 Å. In the fifth C site, C(5) is bonded in a trigonal planar geometry to one C(4), one C(6), and one C(8) atom. The C(5)-C(6) bond length is 1.40 Å. The C(5)-C(8) bond length is 1.48 Å. In the sixth C site, C(6) is bonded in a distorted single-bond geometry to one C(5) and one H(4) atom. The C(6)-H(4) bond length is 1.09 Å. In the seventh C site, C(7) is bonded in a distorted single-bond geometry to one C(2) and one O(6) atom. The C(7)-O(6) bond length is 1.37 Å. In the eighth C site, C(8) is bonded in a distorted bent 120 degrees geometry to one C(5), one O(3), and one O(4) atom. The C(8)-O(3) bond length is 1.27 Å. The C(8)-O(4) bond length is 1.29 Å. There are four inequivalent H sites. In the first H site, H(1) is bonded in a bent 150 degrees geometry to one O(4) and one O(5) atom. The H(1)-O(4) bond length is 1.54 Å. The H(1)-O(5) bond length is 1.03 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(6) atom. The H(2)-O(6) bond length is 1.00 Å. In the third H site, H(3) is bonded in a single-bond geometry to one C(3) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one Ba(1) and one C(6) 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 distorted single-bond geometry to two equivalent Ba(1) and one C(1) atom. In the third O site, O(3) is bonded in a single-bond geometry to two equivalent Ba(1) and one C(8) atom. In the fourth O site, O(4) is bonded in a distorted water-like geometry to one Ba(1), one C(8), and one H(1) atom. In the fifth O site, O(5) is bonded in a distorted water-like geometry to one Ba(1), one C(4), and one H(1) atom. In the sixth O site, O(6) is bonded in a distorted water-like geometry to one Ba(1), one C(7), and one H(2) atom. Linkers: 2 [O]C(=O)c1cc(O)c(C([O])=O)cc1O. Metal clusters: 2 [Ba]. RCSR code: pcu. The MOF has largest included sphere 1.14 A, density 2.82 g/cm3, surface area 1976.43 m2/g, accessible volume 0.02 cm3/g