MnH4(CO3)2 crystallizes in the monoclinic C2/c space group. Mn(1) is bonded in an octahedral geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. Both Mn(1)-O(1) bond lengths are 2.21 Å. Both Mn(1)-O(2) bond lengths are 2.19 Å. Both Mn(1)-O(3) bond lengths are 2.17 Å. 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 1.27 Å. The C(1)-O(2) bond length is 1.27 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(1) and one O(3) atom. The H(1)-O(1) bond length is 1.74 Å. The H(1)-O(3) bond length is 0.99 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(2) and one O(3) atom. The H(2)-O(2) bond length is 1.75 Å. The H(2)-O(3) bond length is 0.99 Å. There are three inequivalent O sites. In the first O site, O(2) is bonded in a 3-coordinate geometry to one Mn(1), one C(1), and one H(2) atom. In the second O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Mn(1), one H(1), and one H(2) atom. In the third O site, O(1) is bonded in a 3-coordinate geometry to one Mn(1), one C(1), and one H(1) atom. Linkers: 2 [O]C(=O)C([O])=O. Metal clusters: 2 [Mn]. The MOF has largest included sphere 1.40 A, density 2.26 g/cm3, surface area 3304.82 m2/g, accessible volume 0.08 cm3/g