CaH18(CO)10 is Indium-like structured and crystallizes in the tetragonal P4_32_12 space group. The structure is zero-dimensional and consists of four CaH18(CO)10 clusters. Ca(1) is bonded in a 10-coordinate geometry to two equivalent H(7), two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. Both Ca(1)-H(7) bond lengths are 2.48 Å. Both Ca(1)-O(1) bond lengths are 2.59 Å. Both Ca(1)-O(2) bond lengths are 2.48 Å. Both Ca(1)-O(3) bond lengths are 2.46 Å. Both Ca(1)-O(4) bond lengths are 2.34 Å. There are five inequivalent C sites. In the first C site, C(1) is bonded in a distorted trigonal non-coplanar geometry to one H(1), one O(1), and one O(5) atom. The C(1)-H(1) bond length is 1.10 Å. The C(1)-O(1) bond length is 1.42 Å. The C(1)-O(5) bond length is 1.42 Å. In the second C site, C(2) is bonded in a distorted water-like geometry to one H(2) and one O(2) atom. The C(2)-H(2) bond length is 1.09 Å. The C(2)-O(2) bond length is 1.45 Å. In the third C site, C(3) is bonded in a distorted water-like geometry to one H(3) and one O(3) atom. The C(3)-H(3) bond length is 1.10 Å. The C(3)-O(3) bond length is 1.44 Å. In the fourth C site, C(4) is bonded in a distorted bent 120 degrees geometry to one H(4) and one O(4) atom. The C(4)-H(4) bond length is 1.11 Å. The C(4)-O(4) bond length is 1.40 Å. In the fifth C site, C(5) is bonded in a distorted trigonal non-coplanar geometry to one H(5), one H(6), and one O(5) atom. The C(5)-H(5) bond length is 1.11 Å. The C(5)-H(6) bond length is 1.10 Å. The C(5)-O(5) bond length is 1.45 Å. There are nine inequivalent H sites. In the first H site, H(1) 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(2) atom. In the third H site, H(3) is bonded in a single-bond geometry to one C(3) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one C(4) atom. In the fifth H site, H(5) is bonded in a single-bond geometry to one C(5) atom. In the sixth H site, H(6) is bonded in a single-bond geometry to one C(5) atom. In the seventh H site, H(7) is bonded in a distorted single-bond geometry to one Ca(1), one O(1), and one O(4) atom. The H(7)-O(1) bond length is 1.03 Å. The H(7)-O(4) bond length is 1.61 Å. In the eighth H site, H(8) is bonded in a single-bond geometry to one O(2) atom. The H(8)-O(2) bond length is 0.98 Å. In the ninth H site, H(9) is bonded in a single-bond geometry to one O(3) atom. The H(9)-O(3) bond length is 0.98 Å. There are five inequivalent O sites. In the first O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one C(3), and one H(9) atom. In the second O site, O(4) is bonded in a 3-coordinate geometry to one Ca(1), one C(4), and one H(7) atom. In the third O site, O(5) is bonded in a bent 120 degrees geometry to one C(1) and one C(5) atom. In the fourth O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one C(1), and one H(7) atom. In the fifth O site, O(2) is bonded in a distorted water-like geometry to one Ca(1), one C(2), and one H(8) atom. Linkers: 8 [O][C@H]1CO[C@H](O)[C@H](O)[C@H]1O. Metal clusters: 4 [Ca]. The MOF has largest included sphere 3.48 A, density 1.36 g/cm3, surface area 3772.09 m2/g, accessible volume 0.22 cm3/g