K2C6N7H3O4 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 7-coordinate geometry to one N(3), one N(4), one N(6), one O(1), one O(2), one O(3), and one O(4) atom. The K(1)-N(3) bond length is 3.13 Å. The K(1)-N(4) bond length is 2.87 Å. The K(1)-N(6) bond length is 3.23 Å. The K(1)-O(1) bond length is 2.63 Å. The K(1)-O(2) bond length is 2.70 Å. The K(1)-O(3) bond length is 2.80 Å. The K(1)-O(4) bond length is 2.79 Å. In the second K site, K(2) is bonded in a 9-coordinate geometry to one N(2), one N(3), one N(6), one H(2), one O(2), one O(3), one O(4), and two equivalent O(1) atoms. The K(2)-N(2) bond length is 3.06 Å. The K(2)-N(3) bond length is 3.15 Å. The K(2)-N(6) bond length is 3.10 Å. The K(2)-H(2) bond length is 2.92 Å. The K(2)-O(2) bond length is 2.78 Å. The K(2)-O(3) bond length is 2.99 Å. The K(2)-O(4) bond length is 2.75 Å. There is one shorter (2.85 Å) and one longer (2.91 Å) K(2)-O(1) bond length. There are six 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 N(7) atom. The C(1)-N(1) bond length is 1.41 Å. The C(1)-N(2) bond length is 1.32 Å. The C(1)-N(7) bond length is 1.33 Å. In the second C site, C(2) is bonded in a trigonal planar geometry to one N(2), one N(3), and one O(1) atom. The C(2)-N(2) bond length is 1.37 Å. The C(2)-N(3) bond length is 1.38 Å. The C(2)-O(1) bond length is 1.26 Å. In the third C site, C(3) is bonded in a trigonal planar geometry to one N(1), one N(3), and one N(4) atom. The C(3)-N(1) bond length is 1.41 Å. The C(3)-N(3) bond length is 1.32 Å. The C(3)-N(4) bond length is 1.33 Å. In the fourth C site, C(4) is bonded in a trigonal planar geometry to one N(4), one N(5), and one O(2) atom. The C(4)-N(4) bond length is 1.35 Å. The C(4)-N(5) bond length is 1.40 Å. The C(4)-O(2) bond length is 1.26 Å. In the fifth C site, C(5) is bonded in a trigonal planar geometry to one N(1), one N(5), and one N(6) atom. The C(5)-N(1) bond length is 1.38 Å. The C(5)-N(5) bond length is 1.35 Å. The C(5)-N(6) bond length is 1.31 Å. In the sixth C site, C(6) is bonded in a trigonal planar geometry to one N(6), one N(7), and one O(3) atom. The C(6)-N(6) bond length is 1.39 Å. The C(6)-N(7) bond length is 1.36 Å. The C(6)-O(3) bond length is 1.27 Å. There are seven inequivalent N sites. In the first N site, N(1) is bonded in a trigonal planar geometry to one C(1), one C(3), and one C(5) atom. In the second N site, N(2) is bonded in a bent 120 degrees geometry to one K(2), one C(1), and one C(2) atom. In the third N site, N(3) is bonded in a bent 120 degrees geometry to one K(1), one K(2), one C(2), and one C(3) atom. In the fourth N site, N(4) is bonded in a distorted bent 120 degrees geometry to one K(1), one C(3), and one C(4) atom. In the fifth N site, N(5) is bonded in a trigonal planar geometry to one C(4), one C(5), and one H(1) atom. The N(5)-H(1) bond length is 1.05 Å. In the sixth N site, N(6) is bonded in a distorted bent 120 degrees geometry to one K(1), one K(2), one C(5), and one C(6) atom. In the seventh N site, N(7) is bonded in a bent 120 degrees geometry to one C(1) and one C(6) atom. There are three inequivalent H sites. In the first H site, H(1) is bonded in a distorted linear geometry to one N(5) and one O(3) atom. The H(1)-O(3) bond length is 1.64 Å. In the second H site, H(2) is bonded in a single-bond geometry to one K(2) and one O(4) atom. The H(2)-O(4) bond length is 0.98 Å. In the third H site, H(3) is bonded in a single-bond geometry to one O(4) atom. The H(3)-O(4) bond length is 0.99 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one K(1), two equivalent K(2), and one C(2) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one K(1), one K(2), and one C(4) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one K(1), one K(2), one C(6), and one H(1) atom. In the fourth O site, O(4) is bonded in a water-like geometry to one K(1), one K(2), one H(2), and one H(3) atom. Linkers: 1 O=C1[N]c2nc(=O)nc3n2C(=N1)NC(=O)[N]3 ,1 O=C1[N]c2nc(=O)nc3n2C(=N1)[N]C(=O)N3 ,1 O=C1[N]C2=NC(=O)NC3=NC(=O)[N]C(=N1)N23 ,1 O=C1[N]c2nc(=O)nc3[nH]c(=O)nc(n23)[N]1. Metal clusters: 8 [K]. The MOF has largest included sphere 1.29 A, density 2.01 g/cm3, surface area 1233.32 m2/g, accessible volume 0.01 cm3/g