BaC5N2H4O5 crystallizes in the monoclinic P2_1/c space group. Ba(1) is bonded in a 9-coordinate geometry to one N(2), one O(2), one O(5), two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms. The Ba(1)-N(2) bond length is 2.84 Å. The Ba(1)-O(2) bond length is 2.94 Å. The Ba(1)-O(5) bond length is 2.88 Å. There is one shorter (2.72 Å) and one longer (2.81 Å) Ba(1)-O(1) bond length. There is one shorter (2.87 Å) and one longer (2.92 Å) Ba(1)-O(3) bond length. There is one shorter (2.81 Å) and one longer (2.92 Å) Ba(1)-O(4) bond length. There are five inequivalent C sites. In the first C site, C(4) is bonded in a distorted single-bond geometry to one C(1), one C(2), and one N(1) atom. The C(4)-C(1) bond length is 1.48 Å. The C(4)-C(2) bond length is 1.39 Å. The C(4)-N(1) bond length is 1.37 Å. In the second C site, C(5) is bonded in a distorted bent 120 degrees geometry to one C(3), one O(1), and one O(2) atom. The C(5)-C(3) bond length is 1.48 Å. The C(5)-O(1) bond length is 1.28 Å. The C(5)-O(2) bond length is 1.28 Å. In the third C site, C(1) is bonded in a distorted bent 120 degrees geometry to one C(4), one O(3), and one O(5) atom. The C(1)-O(3) bond length is 1.28 Å. The C(1)-O(5) bond length is 1.28 Å. In the fourth C site, C(2) is bonded in a distorted single-bond geometry to one C(3), one C(4), and one H(3) atom. The C(2)-C(3) bond length is 1.40 Å. The C(2)-H(3) bond length is 1.08 Å. In the fifth C site, C(3) is bonded in a distorted single-bond geometry to one C(2), one C(5), and one N(2) atom. The C(3)-N(2) bond length is 1.35 Å. There are two inequivalent N sites. In the first N site, N(1) is bonded in a 3-coordinate geometry to one C(4), one N(2), and one H(1) atom. The N(1)-N(2) bond length is 1.33 Å. The N(1)-H(1) bond length is 1.05 Å. In the second N site, N(2) is bonded in a 3-coordinate geometry to one Ba(1), one C(3), and one N(1) atom. There are four inequivalent H sites. In the first H site, H(1) is bonded in a distorted linear geometry to one N(1) and one O(5) atom. The H(1)-O(5) bond length is 1.67 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 1.01 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 O(4) atom. The H(4)-O(4) bond length is 0.97 Å. There are five inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Ba(1), one C(1), and one H(1) atom. In the second O site, O(4) is bonded in a water-like geometry to two equivalent Ba(1), one H(2), and one H(4) atom. In the third O site, O(1) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one C(5) atom. In the fourth O site, O(2) is bonded in a distorted single-bond geometry to one Ba(1) and one C(5) atom. In the fifth O site, O(3) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one C(1) atom. Linkers: 4 [O]C(=O)c1cc(C([O])=O)[nH]n1. Metal clusters: 4 [Ba]. The MOF has largest included sphere 1.51 A, density 2.71 g/cm3, surface area 2307.24 m2/g, accessible volume 0.04 cm3/g