CaC7H11O8CNH2 crystallizes in the trigonal R-3 space group. The structure consists of eighteen methylamine molecules inside a CaC7H11O8 framework. In the CaC7H11O8 framework, Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom. The Ca(1)-O(1) bond length is 2.53 Å. The Ca(1)-O(2) bond length is 2.51 Å. The Ca(1)-O(3) bond length is 2.51 Å. The Ca(1)-O(4) bond length is 2.79 Å. The Ca(1)-O(5) bond length is 2.39 Å. The Ca(1)-O(6) bond length is 2.39 Å. The Ca(1)-O(7) bond length is 2.38 Å. The Ca(1)-O(8) bond length is 2.43 Å. There are seven inequivalent C sites. In the first C site, C(2) is bonded in a trigonal planar geometry to one C(1), one C(3), and one C(7) atom. The C(2)-C(1) bond length is 1.50 Å. The C(2)-C(3) bond length is 1.40 Å. The C(2)-C(7) bond length is 1.40 Å. In the second C site, C(3) is bonded in a distorted single-bond geometry to one C(2), one C(4), and one H(1) atom. The C(3)-C(4) bond length is 1.40 Å. The C(3)-H(1) bond length is 1.09 Å. In the third C site, C(4) is bonded in a trigonal planar geometry to one C(3), one C(5), and one C(8) atom. The C(4)-C(5) bond length is 1.40 Å. The C(4)-C(8) bond length is 1.51 Å. In the fourth C site, C(5) is bonded in a distorted single-bond geometry to one C(4) and one H(3) atom. The C(5)-H(3) bond length is 1.09 Å. In the fifth C site, C(7) is bonded in a distorted single-bond geometry to one C(2) and one H(2) atom. The C(7)-H(2) bond length is 1.09 Å. In the sixth C site, C(8) is bonded in a distorted bent 120 degrees geometry to one C(4), one O(3), and one O(4) atom. The C(8)-O(3) bond length is 1.28 Å. The C(8)-O(4) bond length is 1.27 Å. In the seventh C site, C(1) is bonded in a bent 120 degrees geometry to one C(2), one O(1), and one O(2) atom. The C(1)-O(1) bond length is 1.28 Å. The C(1)-O(2) bond length is 1.28 Å. There are eleven 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(7) 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(6) is bonded in a distorted single-bond geometry to one O(1) and one O(5) atom. The H(6)-O(1) bond length is 1.65 Å. The H(6)-O(5) bond length is 1.00 Å. In the fifth H site, H(7) is bonded in a distorted single-bond geometry to one O(3) and one O(5) atom. The H(7)-O(3) bond length is 1.63 Å. The H(7)-O(5) bond length is 1.00 Å. In the sixth H site, H(8) is bonded in a single-bond geometry to one O(6) atom. The H(8)-O(6) bond length is 0.99 Å. In the seventh H site, H(9) is bonded in a distorted single-bond geometry to one O(4) and one O(6) atom. The H(9)-O(4) bond length is 1.63 Å. The H(9)-O(6) bond length is 1.01 Å. In the eighth H site, H(10) is bonded in a single-bond geometry to one O(7) atom. The H(10)-O(7) bond length is 1.00 Å. In the ninth H site, H(11) is bonded in a single-bond geometry to one O(7) atom. The H(11)-O(7) bond length is 0.99 Å. In the tenth H site, H(12) is bonded in a single-bond geometry to one O(8) atom. The H(12)-O(8) bond length is 1.00 Å. In the eleventh H site, H(13) is bonded in a single-bond geometry to one O(8) atom. The H(13)-O(8) bond length is 0.97 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one C(1), and one H(6) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Ca(1) and one C(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one C(8), and one H(7) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one Ca(1), one C(8), and one H(9) atom. In the fifth O site, O(5) is bonded in a distorted water-like geometry to one Ca(1), one H(6), and one H(7) atom. In the sixth O site, O(6) is bonded in a distorted water-like geometry to one Ca(1), one H(8), and one H(9) atom. In the seventh O site, O(7) is bonded in a distorted water-like geometry to one Ca(1), one H(10), and one H(11) atom. In the eighth O site, O(8) is bonded in a distorted water-like geometry to one Ca(1), one H(12), and one H(13) atom. Linkers: 6 Nc1cc(C([O])=O)cc(C([O])=O)c1. Metal clusters: 6 O.O.O.O.[Ca].[O][C]=O.[O][C]=O. The MOF has largest included sphere 5.16 A, density 1.44 g/cm3, surface area 4304.98 m2/g, accessible volume 0.21 cm3/g