CaC10N2H10O5 crystallizes in the monoclinic P2_1/c space group. Ca(1) is bonded in a 8-coordinate geometry to one N(1), one O(2), one O(3), one O(4), two equivalent O(1), and two equivalent O(5) atoms. The Ca(1)-N(1) bond length is 2.57 Å. The Ca(1)-O(2) bond length is 2.46 Å. The Ca(1)-O(3) bond length is 2.55 Å. The Ca(1)-O(4) bond length is 2.42 Å. There is one shorter (2.47 Å) and one longer (2.50 Å) Ca(1)-O(1) bond length. There is one shorter (2.37 Å) and one longer (2.52 Å) Ca(1)-O(5) bond length. There are ten inequivalent C sites. In the first C site, C(1) is bonded in a trigonal planar geometry to one C(4), one C(5), and one C(6) atom. The C(1)-C(4) bond length is 1.40 Å. The C(1)-C(5) bond length is 1.40 Å. The C(1)-C(6) bond length is 1.50 Å. In the second C site, C(2) is bonded in a distorted trigonal planar geometry to one C(3), one C(7), and one N(1) atom. The C(2)-C(3) bond length is 1.40 Å. The C(2)-C(7) bond length is 1.52 Å. The C(2)-N(1) bond length is 1.35 Å. In the third C site, C(3) is bonded in a distorted single-bond geometry to one C(2) and one H(1) atom. The C(3)-H(1) bond length is 1.08 Å. In the fourth C site, C(4) is bonded in a distorted trigonal planar geometry to one C(1), one N(1), and one H(2) atom. The C(4)-N(1) bond length is 1.34 Å. The C(4)-H(2) bond length is 1.09 Å. In the fifth C site, C(5) is bonded in a distorted single-bond geometry to one C(1) and one H(3) atom. The C(5)-H(3) 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(1), one O(3), and one O(5) atom. The C(6)-O(3) bond length is 1.27 Å. The C(6)-O(5) bond length is 1.27 Å. In the seventh C site, C(7) is bonded in a distorted bent 120 degrees geometry to one C(2), one O(1), and one O(2) atom. The C(7)-O(1) bond length is 1.28 Å. The C(7)-O(2) bond length is 1.26 Å. In the eighth C site, C(8) is bonded in a trigonal planar geometry to one N(2), one H(4), and one O(4) atom. The C(8)-N(2) bond length is 1.34 Å. The C(8)-H(4) bond length is 1.11 Å. The C(8)-O(4) bond length is 1.25 Å. In the ninth C site, C(9) is bonded to one N(2), one H(5), one H(6), and one H(7) atom to form corner-sharing CH3N tetrahedra. The C(9)-N(2) bond length is 1.45 Å. The C(9)-H(5) bond length is 1.10 Å. The C(9)-H(6) bond length is 1.10 Å. The C(9)-H(7) bond length is 1.10 Å. In the tenth C site, C(10) is bonded to one N(2), one H(10), one H(8), and one H(9) atom to form corner-sharing CH3N tetrahedra. The C(10)-N(2) bond length is 1.45 Å. The C(10)-H(10) bond length is 1.10 Å. The C(10)-H(8) bond length is 1.10 Å. The C(10)-H(9) bond length is 1.10 Å. There are two inequivalent N sites. In the first N site, N(1) is bonded in a distorted trigonal planar geometry to one Ca(1), one C(2), and one C(4) atom. In the second N site, N(2) is bonded in a trigonal planar geometry to one C(10), one C(8), and one C(9) atom. There are ten inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one C(3) atom. In the second H site, H(2) is bonded in a single-bond geometry to one C(4) atom. In the third H site, H(3) is bonded in a single-bond geometry to one C(5) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one C(8) atom. In the fifth H site, H(5) is bonded in a single-bond geometry to one C(9) atom. In the sixth H site, H(6) is bonded in a single-bond geometry to one C(9) atom. In the seventh H site, H(7) is bonded in a single-bond geometry to one C(9) atom. In the eighth H site, H(8) is bonded in a single-bond geometry to one C(10) atom. In the ninth H site, H(9) is bonded in a single-bond geometry to one C(10) atom. In the tenth H site, H(10) is bonded in a single-bond geometry to one C(10) atom. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to two equivalent Ca(1) and one C(7) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Ca(1) and one C(7) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Ca(1) and one C(6) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Ca(1) and one C(8) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Ca(1) and one C(6) atom. Linkers: 4 [O]C(=O)c1ccc(C([O])=O)nc1. Metal clusters: 4 [Ca]. The MOF has largest included sphere 2.15 A, density 1.65 g/cm3, surface area 3981.64 m2/g, accessible volume 0.08 cm3/g