KC4N3H4O5 crystallizes in the monoclinic P2_1/c space group. K(1) is bonded in a 7-coordinate geometry to one N(2), one O(1), one O(2), one O(3), one O(4), and two equivalent O(5) atoms. The K(1)-N(2) bond length is 2.87 Å. The K(1)-O(1) bond length is 2.83 Å. The K(1)-O(2) bond length is 2.93 Å. The K(1)-O(3) bond length is 2.73 Å. The K(1)-O(4) bond length is 2.82 Å. There is one shorter (2.76 Å) and one longer (2.86 Å) K(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 C(2), one O(1), and one O(2) atom. The C(4)-C(2) bond length is 1.49 Å. The C(4)-O(1) bond length is 1.26 Å. The C(4)-O(2) bond length is 1.29 Å. In the second C site, C(1) is bonded in a distorted single-bond geometry to one C(2), one C(3), and one N(1) atom. The C(1)-C(2) bond length is 1.40 Å. The C(1)-C(3) bond length is 1.49 Å. The C(1)-N(1) bond length is 1.35 Å. In the third C site, C(2) is bonded in a distorted single-bond geometry to one C(1), one C(4), and one N(3) atom. The C(2)-N(3) bond length is 1.37 Å. In the fourth C site, C(3) is bonded in a distorted bent 120 degrees geometry to one C(1), one O(3), and one O(4) atom. The C(3)-O(3) bond length is 1.30 Å. The C(3)-O(4) bond length is 1.24 Å. There are three inequivalent N sites. In the first N site, N(1) is bonded in a 3-coordinate geometry to one C(1), one N(2), and one H(4) atom. The N(1)-N(2) bond length is 1.34 Å. The N(1)-H(4) bond length is 1.07 Å. In the second N site, N(2) is bonded in a trigonal planar geometry to one K(1), one N(1), and one N(3) atom. The N(2)-N(3) bond length is 1.32 Å. In the third N site, N(3) is bonded in a distorted water-like geometry to one C(2) and one N(2) atom. There are four inequivalent H sites. In the first H site, H(1) is bonded in a linear geometry to one O(2) and one O(3) atom. The H(1)-O(2) bond length is 1.25 Å. The H(1)-O(3) bond length is 1.17 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(5) atom. The H(2)-O(5) bond length is 0.99 Å. In the third H site, H(3) is bonded in a single-bond geometry to one O(5) atom. The H(3)-O(5) bond length is 0.98 Å. In the fourth H site, H(4) is bonded in a linear geometry to one N(1) and one O(1) atom. The H(4)-O(1) bond length is 1.62 Å. There are five inequivalent O sites. In the first O site, O(5) is bonded in a water-like geometry to two equivalent K(1), one H(2), and one H(3) atom. In the second O site, O(4) is bonded in a distorted single-bond geometry to one K(1) and one C(3) atom. In the third O site, O(1) is bonded in a 3-coordinate geometry to one K(1), one C(4), and one H(4) atom. In the fourth O site, O(2) is bonded in a distorted bent 120 degrees geometry to one K(1), one C(4), and one H(1) atom. In the fifth O site, O(3) is bonded in a distorted water-like geometry to one K(1), one C(3), and one H(1) atom. Linkers: 4 [O]C(=O)c1nn[nH]c1C(=O)O. Metal clusters: 4 [K]. The MOF has largest included sphere 1.26 A, density 1.86 g/cm3, surface area 2102.71 m2/g, accessible volume 0.03 cm3/g