NiC9N3H8O4 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a square pyramidal geometry to one N(2), two equivalent O(1), and two equivalent O(2) atoms. The Ni(1)-N(2) bond length is 2.00 Å. Both Ni(1)-O(1) bond lengths are 2.07 Å. Both Ni(1)-O(2) bond lengths are 2.03 Å. In the second Ni site, Ni(2) is bonded to two equivalent N(1), two equivalent N(3), and two equivalent O(4) atoms to form corner-sharing NiN4O2 octahedra. The corner-sharing octahedral tilt angles are 57°. Both Ni(2)-N(1) bond lengths are 2.08 Å. Both Ni(2)-N(3) bond lengths are 2.10 Å. Both Ni(2)-O(4) bond lengths are 2.06 Å. There are ten inequivalent C sites. In the first C site, C(1) is bonded in a distorted trigonal planar geometry to one C(2), one N(1), and one H(3) atom. The C(1)-C(2) bond length is 1.39 Å. The C(1)-N(1) bond length is 1.35 Å. The C(1)-H(3) bond length is 1.09 Å. In the second C site, C(2) is bonded in a distorted single-bond geometry to one C(1), one C(3), and one H(4) atom. The C(2)-C(3) bond length is 1.40 Å. The C(2)-H(4) bond length is 1.09 Å. In the third C site, C(3) is bonded in a trigonal planar geometry to one C(2), one C(4), and one C(6) atom. The C(3)-C(4) bond length is 1.40 Å. The C(3)-C(6) bond length is 1.50 Å. In the fourth C site, C(4) is bonded in a distorted trigonal planar geometry to one C(3), one C(5), and one H(5) atom. The C(4)-C(5) bond length is 1.39 Å. The C(4)-H(5) bond length is 1.09 Å. In the fifth C site, C(5) is bonded in a distorted bent 120 degrees geometry to one C(4), one N(1), and one H(6) atom. The C(5)-N(1) bond length is 1.35 Å. The C(5)-H(6) bond length is 1.09 Å. In the sixth C site, C(6) is bonded in a distorted bent 120 degrees geometry to one C(3), one O(2), and one O(3) atom. The C(6)-O(2) bond length is 1.28 Å. The C(6)-O(3) bond length is 1.27 Å. In the seventh C site, C(7) is bonded in a distorted trigonal planar geometry to one C(8), one N(2), and one H(7) atom. The C(7)-C(8) bond length is 1.39 Å. The C(7)-N(2) bond length is 1.35 Å. The C(7)-H(7) bond length is 1.09 Å. In the eighth C site, C(8) is bonded in a distorted single-bond geometry to one C(7), one C(9), and one H(8) atom. The C(8)-C(9) bond length is 1.40 Å. The C(8)-H(8) bond length is 1.09 Å. In the ninth C site, C(9) is bonded in a trigonal planar geometry to one C(10) and two equivalent C(8) atoms. The C(9)-C(10) bond length is 1.51 Å. In the tenth C site, C(10) is bonded in a distorted bent 120 degrees geometry to one C(9) and two equivalent O(4) atoms. Both C(10)-O(4) bond lengths are 1.27 Å. There are five inequivalent N sites. In the first N site, N(1) is bonded in a trigonal planar geometry to one Ni(2), one C(1), and one C(5) atom. In the second N site, N(2) is bonded in a trigonal planar geometry to one Ni(1) and two equivalent C(7) atoms. In the third N site, N(3) is bonded in a trigonal planar geometry to two equivalent Ni(2) and one N(4) atom. The N(3)-N(4) bond length is 1.21 Å. In the fourth N site, N(4) is bonded in a linear geometry to one N(3) and one N(5) atom. The N(4)-N(5) bond length is 1.17 Å. In the fifth N site, N(5) is bonded in a single-bond geometry to one N(4) atom. There are eight 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 0.99 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 0.99 Å. In the third H site, H(3) is bonded in a single-bond geometry to one C(1) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one C(2) atom. In the fifth H site, H(5) is bonded in a single-bond geometry to one C(4) atom. In the sixth H site, H(6) is bonded in a single-bond geometry to one C(5) atom. In the seventh H site, H(7) is bonded in a single-bond geometry to one C(7) atom. In the eighth H site, H(8) is bonded in a single-bond geometry to one C(8) atom. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ni(1), one H(1), and one H(2) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Ni(1) and one C(6) atom. In the third O site, O(3) is bonded in a single-bond geometry to one C(6) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Ni(2) and one C(10) atom. Linkers: 6 [O]C(=O)c1ccncc1. Metal clusters: 2 O.O.O=[C]O[Ni]O[C]=O ,2 [Ni]. The MOF has largest included sphere 5.09 A, density 1.36 g/cm3, surface area 4099.77 m2/g, accessible volume 0.24 cm3/g