NaC4N5H6O4 crystallizes in the monoclinic P2_1/c space group. Na(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form edge-sharing NaO6 octahedra. The Na(1)-O(1) bond length is 2.56 Å. The Na(1)-O(4) bond length is 2.38 Å. There is one shorter (2.39 Å) and one longer (2.48 Å) Na(1)-O(2) bond length. There is one shorter (2.44 Å) and one longer (2.50 Å) Na(1)-O(3) bond length. There are four inequivalent C sites. In the first C site, C(1) is bonded in a 3-coordinate geometry to one C(2), one N(1), and one N(2) atom. The C(1)-C(2) bond length is 1.46 Å. The C(1)-N(1) bond length is 1.36 Å. The C(1)-N(2) bond length is 1.30 Å. In the second C site, C(2) is bonded in a distorted trigonal planar geometry to one C(1), one N(4), and one N(5) atom. The C(2)-N(4) bond length is 1.33 Å. The C(2)-N(5) bond length is 1.34 Å. In the third C site, C(3) is bonded in a trigonal planar geometry to one N(3), one N(4), and one O(3) atom. The C(3)-N(3) bond length is 1.38 Å. The C(3)-N(4) bond length is 1.37 Å. The C(3)-O(3) bond length is 1.27 Å. In the fourth C site, C(4) is bonded in a trigonal planar geometry to one N(1), one N(5), and one O(4) atom. The C(4)-N(1) bond length is 1.40 Å. The C(4)-N(5) bond length is 1.39 Å. The C(4)-O(4) bond length is 1.25 Å. There are five 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(1) atom. The N(1)-H(1) bond length is 1.05 Å. In the second N site, N(2) is bonded in a distorted single-bond geometry to one C(1) atom. In the third N site, N(3) is bonded in a 2-coordinate geometry to one C(3) and one H(6) atom. The N(3)-H(6) bond length is 1.04 Å. In the fourth N site, N(4) is bonded in a distorted trigonal planar geometry to one C(2), one C(3), and one H(3) atom. The N(4)-H(3) bond length is 1.74 Å. In the fifth N site, N(5) is bonded in a water-like geometry to one C(2) and one C(4) atom. There are six inequivalent H sites. In the first H site, H(1) is bonded in a distorted single-bond geometry to one N(1) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(1) atom. The H(2)-O(1) bond length is 0.99 Å. In the third H site, H(3) is bonded in a single-bond geometry to one N(4) and one O(1) atom. The H(3)-O(1) bond length is 1.01 Å. In the fourth H site, H(4) is bonded in a single-bond geometry to one O(2) atom. The H(4)-O(2) bond length is 0.99 Å. In the fifth H site, H(5) is bonded in a single-bond geometry to one O(2) atom. The H(5)-O(2) bond length is 1.00 Å. In the sixth H site, H(6) is bonded in a distorted single-bond geometry to one N(3) and one O(4) atom. The H(6)-O(4) bond length is 1.71 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a water-like geometry to one Na(1), one H(2), and one H(3) atom. In the second O site, O(2) is bonded in a distorted water-like geometry to two equivalent Na(1), one H(4), and one H(5) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to two equivalent Na(1) and one C(3) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one C(4), and one H(6) atom. Linkers: 4 O=C1[N]c2nc(=O)[nH]nc2N1. Metal clusters: 4 [Na]. RCSR code: fes. The MOF has largest included sphere 1.71 A, density 1.84 g/cm3, surface area 2978.90 m2/g, accessible volume 0.10 cm3/g