CaC4H12(N3O2)4 crystallizes in the monoclinic C2/c space group. Ca(1) is bonded in a 8-coordinate geometry to two equivalent N(2), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. Both Ca(1)-N(2) bond lengths are 2.52 Å. Both Ca(1)-O(1) bond lengths are 2.37 Å. Both Ca(1)-O(2) bond lengths are 2.46 Å. Both Ca(1)-O(3) bond lengths are 2.48 Å. There are two inequivalent C sites. In the first C site, C(1) is bonded in a trigonal planar geometry to one N(1), one N(3), and one N(4) atom. The C(1)-N(1) bond length is 1.38 Å. The C(1)-N(3) bond length is 1.34 Å. The C(1)-N(4) bond length is 1.34 Å. In the second C site, C(2) is bonded in a distorted trigonal planar geometry to one C(2), one N(1), and one N(5) atom. The C(2)-C(2) bond length is 1.44 Å. The C(2)-N(1) bond length is 1.39 Å. The C(2)-N(5) bond length is 1.32 Å. There are six inequivalent N sites. In the first N site, N(1) is bonded in a distorted trigonal planar geometry to one C(1), one C(2), and one N(2) atom. The N(1)-N(2) bond length is 1.37 Å. In the second N site, N(2) is bonded in a distorted T-shaped geometry to one Ca(1), one N(1), and one N(6) atom. The N(2)-N(6) bond length is 1.35 Å. In the third N site, N(3) is bonded in a trigonal planar geometry to one C(1), one H(1), and one H(2) atom. The N(3)-H(1) bond length is 1.02 Å. The N(3)-H(2) bond length is 1.02 Å. In the fourth N site, N(4) is bonded in a distorted trigonal planar geometry to one C(1), one N(5), and one H(4) atom. The N(4)-N(5) bond length is 1.38 Å. The N(4)-H(4) bond length is 1.76 Å. In the fifth N site, N(5) is bonded in a distorted single-bond geometry to one C(2), one N(4), and one H(5) atom. The N(5)-H(5) bond length is 1.79 Å. In the sixth N site, N(6) is bonded in a distorted trigonal planar geometry to one N(2), one O(3), and one O(4) atom. The N(6)-O(3) bond length is 1.29 Å. The N(6)-O(4) bond length is 1.24 Å. There are six inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one N(3) atom. In the second H site, H(2) is bonded in a single-bond geometry to one N(3) atom. In the third H site, H(3) is bonded in a single-bond geometry to one O(2) atom. The H(3)-O(2) bond length is 0.97 Å. In the fourth H site, H(4) is bonded in a single-bond geometry to one N(4) and one O(1) atom. The H(4)-O(1) bond length is 1.01 Å. In the fifth H site, H(5) is bonded in a single-bond geometry to one N(5) and one O(1) atom. The H(5)-O(1) bond length is 1.00 Å. In the sixth H site, H(6) is bonded in a distorted single-bond geometry to one O(2) and one O(3) atom. The H(6)-O(2) bond length is 1.00 Å. The H(6)-O(3) bond length is 1.66 Å. There are four inequivalent O sites. In the first O site, O(4) is bonded in a single-bond geometry to one N(6) atom. In the second O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one H(4), and one H(5) atom. In the third O site, O(2) is bonded in a distorted water-like geometry to one Ca(1), one H(3), and one H(6) atom. In the fourth O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one N(6), and one H(6) atom. Linkers: 2 Nc1nnc(-c2nnc(N)n2[N]N=O)n1[N]N=O. Metal clusters: 2 O.O.O.O.[Ca].[N][N+](=O)[O-].[N][N+](=O)[O-]. The MOF has largest included sphere 2.26 A, density 1.72 g/cm3, surface area 4197.84 m2/g, accessible volume 0.16 cm3/g