NaC4N2H4O3Br crystallizes in the monoclinic C2/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent Br(1) atoms to form distorted edge-sharing NaBr2O4 octahedra. Both Na(1)-O(1) bond lengths are 2.39 Å. Both Na(1)-O(3) bond lengths are 2.43 Å. Both Na(1)-Br(1) bond lengths are 2.92 Å. In the second Na site, Na(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent Br(1) atoms to form distorted edge-sharing NaBr2O4 octahedra. Both Na(2)-O(2) bond lengths are 2.32 Å. Both Na(2)-O(3) bond lengths are 2.38 Å. Both Na(2)-Br(1) bond lengths are 3.02 Å. There are four inequivalent C sites. In the first C site, C(1) is bonded in a trigonal planar geometry to one N(1), one N(2), and one O(1) atom. The C(1)-N(1) bond length is 1.39 Å. The C(1)-N(2) bond length is 1.38 Å. The C(1)-O(1) bond length is 1.24 Å. In the second C site, C(2) is bonded in a distorted bent 120 degrees geometry to one N(2) and one O(2) atom. The C(2)-N(2) bond length is 1.38 Å. The C(2)-O(2) bond length is 1.23 Å. In the third C site, C(3) is bonded in a water-like geometry to one C(4), one H(1), and one H(2) atom. The C(3)-C(4) bond length is 1.50 Å. The C(3)-H(1) bond length is 1.09 Å. The C(3)-H(2) bond length is 1.11 Å. In the fourth C site, C(4) is bonded in a distorted bent 120 degrees geometry to one C(3), one N(1), and one O(3) atom. The C(4)-N(1) bond length is 1.37 Å. The C(4)-O(3) bond length is 1.24 Å. There are two inequivalent N sites. In the first N site, N(1) is bonded in a trigonal planar geometry to one C(1), one C(4), and one H(3) atom. The N(1)-H(3) bond length is 1.04 Å. In the second N site, N(2) is bonded in a trigonal planar geometry to one C(1), one C(2), and one H(4) atom. The N(2)-H(4) bond length is 1.04 Å. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one C(3) atom. In the second H site, H(2) is bonded in a single-bond geometry to one C(3) atom. In the third H site, H(3) is bonded in a single-bond geometry to one N(1) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one N(2) atom. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Na(1) and one C(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Na(2) and one C(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Na(2), and one C(4) atom. Br(1) is bonded in a 2-coordinate geometry to one Na(1) and one Na(2) atom. Linkers: 4 O=C1CC(=O)NC(=O)N1. Metal clusters: 4 [Na]. The MOF has largest included sphere 1.50 A, density 2.18 g/cm3, surface area 2746.52 m2/g, accessible volume 0.06 cm3/g