MgH18(C4O)2 is Indium-like structured and crystallizes in the orthorhombic Pnma space group. The structure is zero-dimensional and consists of four MgH18(C4O)2 clusters. Mg(1) is bonded in a tetrahedral geometry to two equivalent C(1), one O(1), and one O(2) atom. Both Mg(1)-C(1) bond lengths are 2.16 Å. The Mg(1)-O(1) bond length is 2.11 Å. The Mg(1)-O(2) bond length is 2.14 Å. There are four inequivalent C sites. In the first C site, C(4) is bonded in a distorted trigonal non-coplanar geometry to one C(1), one H(3), one H(4), and one H(5) atom. The C(4)-C(1) bond length is 1.54 Å. The C(4)-H(3) bond length is 1.10 Å. The C(4)-H(4) bond length is 1.11 Å. The C(4)-H(5) bond length is 1.10 Å. In the second C site, C(1) is bonded in a distorted water-like geometry to one Mg(1), one C(4), one H(1), and one H(2) atom. The C(1)-H(1) bond length is 1.11 Å. The C(1)-H(2) bond length is 1.11 Å. In the third C site, C(3) is bonded in a distorted trigonal non-coplanar geometry to one H(6), one H(7), and one O(1) atom. The C(3)-H(6) bond length is 1.10 Å. The C(3)-H(7) bond length is 1.09 Å. The C(3)-O(1) bond length is 1.45 Å. In the fourth C site, C(2) is bonded in a distorted trigonal non-coplanar geometry to one H(8), one H(9), and one O(2) atom. The C(2)-H(8) bond length is 1.10 Å. The C(2)-H(9) bond length is 1.10 Å. The C(2)-O(2) 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(5) is bonded in a single-bond geometry to one C(4) atom. In the third H site, H(9) is bonded in a single-bond geometry to one C(2) atom. In the fourth H site, H(2) is bonded in a single-bond geometry to one C(1) atom. In the fifth H site, H(6) is bonded in a single-bond geometry to one C(3) atom. In the sixth H site, H(8) is bonded in a single-bond geometry to one C(2) atom. In the seventh H site, H(3) is bonded in a single-bond geometry to one C(4) atom. In the eighth H site, H(7) is bonded in a single-bond geometry to one C(3) atom. In the ninth H site, H(4) is bonded in a single-bond geometry to one C(4) atom. There are two inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Mg(1) and two equivalent C(3) atoms. In the second O site, O(2) is bonded in a trigonal planar geometry to one Mg(1) and two equivalent C(2) atoms. Linkers: 4 C1COCCO1. Metal clusters: 4 [Mg]. The MOF has largest included sphere 2.08 A, density 1.19 g/cm3, surface area 7229.59 m2/g, accessible volume 0.18 cm3/g