CaC7NH7O6 crystallizes in the monoclinic Cc space group. Ca(1) is bonded in a pentagonal bipyramidal geometry to one N(1), one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom. The Ca(1)-N(1) bond length is 2.53 Å. The Ca(1)-O(1) bond length is 2.40 Å. The Ca(1)-O(2) bond length is 2.56 Å. The Ca(1)-O(3) bond length is 2.56 Å. The Ca(1)-O(4) bond length is 2.40 Å. The Ca(1)-O(5) bond length is 2.33 Å. The Ca(1)-O(6) bond length is 2.33 Å. There are seven 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(1,3) atom. The C(1)-C(2) bond length is 1.40 Å. The C(1)-N(1) bond length is 1.34 Å. The C(1)-H(1,3) bond length is 1.09 Å. In the second C site, C(2) is bonded in a trigonal planar geometry to one C(1), one C(3), and one C(4) atom. The C(2)-C(3) bond length is 1.50 Å. The C(2)-C(4) bond length is 1.40 Å. In the third C site, C(3) is bonded in a distorted bent 120 degrees geometry to one C(2), one O(1), and one O(2) atom. The C(3)-O(1) bond length is 1.28 Å. The C(3)-O(2) bond length is 1.27 Å. In the fourth C site, C(4) is bonded in a distorted single-bond geometry to one C(2), one C(5), and one H(2) atom. The C(4)-C(5) bond length is 1.40 Å. The C(4)-H(2) bond length is 1.09 Å. In the fifth C site, C(5) is bonded in a trigonal planar geometry to one C(4), one C(6), and one C(7) atom. The C(5)-C(6) bond length is 1.50 Å. The C(5)-C(7) bond length is 1.40 Å. In the sixth C site, C(6) is bonded in a distorted bent 120 degrees geometry to one C(5), one O(3), and one O(4) atom. The C(6)-O(3) bond length is 1.27 Å. The C(6)-O(4) bond length is 1.28 Å. In the seventh C site, C(7) is bonded in a distorted trigonal planar geometry to one C(5); one N(1); and one H(1,3) atom. The C(7)-N(1) bond length is 1.34 Å. The C(7)-H(1,3) bond length is 1.09 Å. N(1) is bonded in a trigonal planar geometry to one Ca(1), one C(1), and one C(7) atom. There are six inequivalent H sites. In the first H site, H(1,3) is bonded in a single-bond geometry to one C(1) 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(4) is bonded in a single-bond geometry to one O(2) and one O(5) atom. The H(4)-O(2) bond length is 1.72 Å. The H(4)-O(5) bond length is 0.99 Å. In the fourth H site, H(5) is bonded in a single-bond geometry to one O(4) and one O(5) atom. The H(5)-O(4) bond length is 1.75 Å. The H(5)-O(5) bond length is 0.99 Å. In the fifth H site, H(6) is bonded in a single-bond geometry to one O(3) and one O(6) atom. The H(6)-O(3) bond length is 1.72 Å. The H(6)-O(6) bond length is 0.99 Å. In the sixth H site, H(7) is bonded in a single-bond geometry to one O(1) and one O(6) atom. The H(7)-O(1) bond length is 1.74 Å. The H(7)-O(6) bond length is 0.99 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one C(3), and one H(7) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Ca(1), one C(3), and one H(4) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Ca(1), one C(6), and one H(6) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ca(1), one C(6), and one H(5) atom. In the fifth O site, O(5) is bonded in a distorted water-like geometry to one Ca(1), one H(4), and one H(5) atom. In the sixth O site, O(6) is bonded in a distorted water-like geometry to one Ca(1), one H(6), and one H(7) atom. Linkers: 2 [O]C(=O)c1cncc(C([O])=O)c1. Metal clusters: 2 O.O.[Ca].[O][C]=O.[O][C]=O. The MOF has largest included sphere 2.01 A, density 1.72 g/cm3, surface area 3800.42 m2/g, accessible volume 0.06 cm3/g