MnH6(CO2)4 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 2.16 Å. Both Mn(1)-O(3) bond lengths are 2.18 Å. There are two inequivalent C sites. In the first C site, C(2) is bonded in a trigonal planar geometry to one H(2), one O(3), and one O(4) atom. The C(2)-H(2) bond length is 1.11 Å. The C(2)-O(3) bond length is 1.24 Å. The C(2)-O(4) bond length is 1.30 Å. In the second C site, C(1) is bonded in a trigonal planar geometry to one H(1), one O(1), and one O(2) atom. The C(1)-H(1) bond length is 1.10 Å. The C(1)-O(1) bond length is 1.29 Å. The C(1)-O(2) bond length is 1.26 Å. There are three 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 linear geometry to one O(1) and one O(4) atom. The H(3)-O(1) bond length is 1.49 Å. The H(3)-O(4) bond length is 1.05 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Mn(1), one C(1), and one H(3) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Mn(1) and one C(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Mn(1) and one C(2) atom. In the fourth O site, O(4) is bonded in a water-like geometry to one C(2) and one H(3) atom. Linkers: 4 [O]C=O. Metal clusters: 2 [Mn]. RCSR code: sql. The MOF has largest included sphere 2.25 A, density 1.80 g/cm3, surface area 3871.66 m2/g, accessible volume 0.14 cm3/g