KC4N9H4O5 crystallizes in the monoclinic P2_1/c space group. K(1) is bonded in a 10-coordinate geometry to one N(1), one N(2), one H(4), one O(1), one O(2), one O(5), two equivalent O(3), and two equivalent O(4) atoms. The K(1)-N(1) bond length is 2.99 Å. The K(1)-N(2) bond length is 2.84 Å. The K(1)-H(4) bond length is 2.96 Å. The K(1)-O(1) bond length is 2.88 Å. The K(1)-O(2) bond length is 2.81 Å. The K(1)-O(5) bond length is 3.11 Å. There is one shorter (3.00 Å) and one longer (3.19 Å) K(1)-O(3) bond length. There is one shorter (2.80 Å) and one longer (2.98 Å) K(1)-O(4) bond length. 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(4), and one N(5) atom. The C(1)-N(1) bond length is 1.34 Å. The C(1)-N(4) bond length is 1.38 Å. The C(1)-N(5) bond length is 1.34 Å. In the second C site, C(2) is bonded in a distorted trigonal planar geometry to one C(3), one N(5), and one N(7) atom. The C(2)-C(3) bond length is 1.48 Å. The C(2)-N(5) bond length is 1.35 Å. The C(2)-N(7) bond length is 1.32 Å. In the third C site, C(3) is bonded in a distorted trigonal planar geometry to one C(2), one C(4), and one N(6) atom. The C(3)-C(4) bond length is 1.47 Å. The C(3)-N(6) bond length is 1.31 Å. In the fourth C site, C(4) is bonded in a distorted trigonal planar geometry to one C(3), one N(8), and one N(9) atom. The C(4)-N(8) bond length is 1.39 Å. The C(4)-N(9) bond length is 1.38 Å. There are nine inequivalent N sites. In the first N site, N(1) is bonded in a distorted single-bond geometry to one K(1), one C(1), and one N(2) atom. The N(1)-N(2) bond length is 1.36 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 1.30 Å. In the third N site, N(3) is bonded in a water-like geometry to one N(2) and one N(4) atom. The N(3)-N(4) bond length is 1.36 Å. In the fourth N site, N(4) is bonded in a distorted trigonal planar geometry to one C(1), one N(3), and one N(6) atom. The N(4)-N(6) bond length is 1.33 Å. In the fifth N site, N(5) is bonded in a bent 120 degrees geometry to one C(1) and one C(2) atom. In the sixth N site, N(6) is bonded in a distorted bent 120 degrees geometry to one C(3) and one N(4) atom. In the seventh N site, N(7) is bonded in a trigonal planar geometry to one C(2), one H(1), and one H(2) atom. The N(7)-H(1) bond length is 1.02 Å. The N(7)-H(2) bond length is 1.03 Å. In the eighth N site, N(8) is bonded in a trigonal planar geometry to one C(4), one O(1), and one O(2) atom. The N(8)-O(1) bond length is 1.26 Å. The N(8)-O(2) bond length is 1.26 Å. In the ninth N site, N(9) is bonded in a trigonal planar geometry to one C(4), one O(3), and one O(4) atom. The N(9)-O(3) bond length is 1.26 Å. The N(9)-O(4) bond length is 1.28 Å. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one N(7) atom. In the second H site, H(2) is bonded in a single-bond geometry to one N(7) atom. 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 0.99 Å. In the fourth H site, H(4) is bonded in a single-bond geometry to one K(1) and one O(5) atom. The H(4)-O(5) bond length is 0.98 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one K(1) and one N(8) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one K(1) and one N(8) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to two equivalent K(1) and one N(9) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to two equivalent K(1) and one N(9) atom. In the fifth O site, O(5) is bonded in a water-like geometry to one K(1), one H(3), and one H(4) atom. Linkers: 3 Nc1nc2nnnn2nc1[C]([N+](=O)[O-])[N+](=O)[O-] ,1 N[C]1N=C2[N]N=NN2N=C1[C]([N+](=O)[O-])[N+](=O)[O-]. Metal clusters: 4 [K]. The MOF has largest included sphere 1.65 A, density 1.90 g/cm3, surface area 2499.16 m2/g, accessible volume 0.05 cm3/g