KC2H2(NO)4 crystallizes in the monoclinic P2_1/c space group. K(1) is bonded in a 9-coordinate geometry to one N(3), one O(3), two equivalent O(1), two equivalent O(2), and three equivalent O(4) atoms. The K(1)-N(3) bond length is 2.84 Å. The K(1)-O(3) bond length is 2.98 Å. There is one shorter (2.76 Å) and one longer (2.77 Å) K(1)-O(1) bond length. There is one shorter (2.78 Å) and one longer (2.91 Å) K(1)-O(2) bond length. There are a spread of K(1)-O(4) bond distances ranging from 3.06-3.30 Å. There are two inequivalent C sites. In the first C site, C(1) is bonded in a distorted trigonal planar geometry to one C(1), one N(1), and one N(3) atom. The C(1)-C(1) bond length is 1.43 Å. The C(1)-N(1) bond length is 1.40 Å. The C(1)-N(3) bond length is 1.34 Å. In the second C site, C(2) is bonded in a trigonal planar geometry to one N(2), one N(3), and one N(4) atom. The C(2)-N(2) bond length is 1.35 Å. The C(2)-N(3) bond length is 1.34 Å. The C(2)-N(4) bond length is 1.42 Å. There are four inequivalent N sites. In the first N site, N(4) is bonded in a trigonal planar geometry to one C(2), one O(3), and one O(4) atom. The N(4)-O(3) bond length is 1.25 Å. The N(4)-O(4) bond length is 1.25 Å. In the second N site, N(1) is bonded in a distorted trigonal planar geometry to one C(1), one N(2), and one O(2) atom. The N(1)-N(2) bond length is 1.35 Å. The N(1)-O(2) bond length is 1.29 Å. In the third N site, N(2) is bonded in a distorted water-like geometry to one C(2) and one N(1) atom. In the fourth N site, N(3) is bonded in a distorted water-like geometry to one K(1), one C(1), and one C(2) atom. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(1) atom. The H(1)-O(1) bond length is 0.98 Å. 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 0.98 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a water-like geometry to two equivalent K(1), one H(1), and one H(2) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to two equivalent K(1) and one N(1) atom. In the third O site, O(3) is bonded in a single-bond geometry to one K(1) and one N(4) atom. In the fourth O site, O(4) is bonded in a single-bond geometry to three equivalent K(1) and one N(4) atom. Linkers: 1 [O]N1[N]C([N+](=O)[O-])=N/C1=C1/[N]C([N+](=O)[O-])=NN1[O] ,2 [O]n1n[c]nc1-c1nc([N+](=O)[O-])nn1[O] ,1 [O]n1nc([N+](=O)[O-])nc1-c1nc([N+](=O)[O-])nn1[O]. Metal clusters: 4 [K]. The MOF has largest included sphere 1.28 A, density 2.01 g/cm3, surface area 1751.41 m2/g, accessible volume 0.02 cm3/g