CaC9H6O7 crystallizes in the triclinic P-1 space group. Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(5), one O(6), one O(7), two equivalent O(2), and two equivalent O(4) atoms. The Ca(1)-O(1) bond length is 2.46 Å. The Ca(1)-O(5) bond length is 2.42 Å. The Ca(1)-O(6) bond length is 2.55 Å. The Ca(1)-O(7) bond length is 2.45 Å. There is one shorter (2.46 Å) and one longer (2.52 Å) Ca(1)-O(2) bond length. There is one shorter (2.43 Å) and one longer (2.54 Å) Ca(1)-O(4) bond length. There are nine inequivalent C sites. In the first C site, C(1) is bonded in a trigonal planar geometry to one C(3), one C(6), and one C(8) atom. The C(1)-C(3) bond length is 1.39 Å. The C(1)-C(6) bond length is 1.49 Å. The C(1)-C(8) bond length is 1.40 Å. In the second C site, C(2) is bonded in a trigonal planar geometry to one C(5), one C(7), and one C(8) atom. The C(2)-C(5) bond length is 1.40 Å. The C(2)-C(7) bond length is 1.50 Å. The C(2)-C(8) bond length is 1.40 Å. In the third C site, C(3) is bonded in a distorted trigonal planar geometry to one C(1), one C(9), and one H(2) atom. The C(3)-C(9) bond length is 1.40 Å. The C(3)-H(2) bond length is 1.09 Å. In the fourth C site, C(4) is bonded in a distorted bent 120 degrees geometry to one C(9), one O(3), and one O(5) atom. The C(4)-C(9) bond length is 1.48 Å. The C(4)-O(3) bond length is 1.33 Å. The C(4)-O(5) bond length is 1.24 Å. In the fifth C site, C(5) is bonded in a distorted single-bond geometry to one C(2), one C(9), and one H(3) atom. The C(5)-C(9) bond length is 1.40 Å. 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(1), and one O(6) atom. The C(6)-O(1) bond length is 1.28 Å. The C(6)-O(6) 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(2), and one O(4) atom. The C(7)-O(2) bond length is 1.27 Å. The C(7)-O(4) bond length is 1.28 Å. In the eighth C site, C(8) is bonded in a distorted single-bond geometry to one C(1), one C(2), and one H(4) atom. The C(8)-H(4) bond length is 1.09 Å. In the ninth C site, C(9) is bonded in a trigonal planar geometry to one C(3), one C(4), and one C(5) atom. There are six inequivalent H sites. In the first H site, H(1) is bonded in a distorted linear geometry to one O(1) and one O(3) atom. The H(1)-O(1) bond length is 1.55 Å. The H(1)-O(3) bond length is 1.02 Å. In the second H site, H(2) is bonded in a single-bond geometry to one C(3) 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 O(7) atom. The H(5)-O(7) bond length is 1.00 Å. In the sixth H site, H(6) is bonded in a single-bond geometry to one O(7) atom. The H(6)-O(7) bond length is 0.97 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Ca(1), one C(6), and one H(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Ca(1) and one C(7) atom. In the third O site, O(3) is bonded in a water-like geometry to one C(4) and one H(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Ca(1) and one C(7) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one Ca(1) and one C(4) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Ca(1) and one C(6) atom. In the seventh O site, O(7) is bonded in a distorted water-like geometry to one Ca(1), one H(5), and one H(6) atom. Linkers: 2 [O]C(=O)c1cc(C([O])=O)cc(C(=O)O)c1. Metal clusters: 2 [Ca]. The MOF has largest included sphere 2.74 A, density 1.70 g/cm3, surface area 3266.49 m2/g, accessible volume 0.18 cm3/g