MgH4(CO3)2(CH)2 crystallizes in the trigonal R-3 space group. The structure consists of thirty-six 02329_fluka molecules inside a MgH4(CO3)2 framework. In the MgH4(CO3)2 framework, Mg(1) is bonded in an octahedral geometry to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom. The Mg(1)-O(1) bond length is 2.05 Å. The Mg(1)-O(2) bond length is 2.08 Å. The Mg(1)-O(3) bond length is 2.06 Å. The Mg(1)-O(4) bond length is 2.09 Å. The Mg(1)-O(5) bond length is 2.12 Å. The Mg(1)-O(6) bond length is 2.15 Å. There are two inequivalent C sites. In the first C site, C(4) is bonded in a distorted bent 120 degrees geometry to one O(3) and one O(4) atom. The C(4)-O(3) bond length is 1.26 Å. The C(4)-O(4) bond length is 1.28 Å. In the second C site, C(1) is bonded in a distorted bent 120 degrees geometry to one O(1) and one O(2) atom. The C(1)-O(1) bond length is 1.26 Å. The C(1)-O(2) bond length is 1.28 Å. There are four inequivalent H sites. In the first H site, H(4) is bonded in a single-bond geometry to one O(6) atom. The H(4)-O(6) bond length is 0.99 Å. In the second H site, H(1) is bonded in a single-bond geometry to one O(5) atom. The H(1)-O(5) bond length is 1.00 Å. In the third H site, H(2) is bonded in a single-bond geometry to one O(5) atom. The H(2)-O(5) bond length is 0.98 Å. In the fourth H site, H(3) is bonded in a single-bond geometry to one O(6) atom. The H(3)-O(6) bond length is 1.00 Å. There are six inequivalent O sites. In the first O site, O(6) is bonded in a distorted water-like geometry to one Mg(1), one H(3), and one H(4) atom. In the second O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Mg(1) and one C(1) atom. In the third O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Mg(1) and one C(1) atom. In the fourth O site, O(3) is bonded in a bent 150 degrees geometry to one Mg(1) and one C(4) atom. In the fifth O site, O(5) is bonded in a distorted water-like geometry to one Mg(1), one H(1), and one H(2) atom. In the sixth O site, O(4) is bonded in a bent 120 degrees geometry to one Mg(1) and one C(4) atom. Linkers: 2 [O]C(=O)[C@H]1[C@H](C([O])=O)[C@@H](C([O])=O)[C@H](C([O])=O)[C@@H](C([O])=O)[C@@H]1C([O])=O. Metal clusters: 6 [Mg]. The MOF has largest included sphere 2.96 A, density 2.00 g/cm3, surface area 2751.66 m2/g, accessible volume 0.09 cm3/g