MnH3(CO2)3 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 1.97 Å. Both Mn(1)-O(2) bond lengths are 2.07 Å. Both Mn(1)-O(3) bond lengths are 2.02 Å. There are two inequivalent C sites. In the first 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 1.28 Å. The C(1)-O(2) bond length is 1.26 Å. In the second C site, C(2) is bonded in a trigonal planar geometry to one H(2) and two equivalent O(3) atoms. The C(2)-H(2) bond length is 1.10 Å. Both C(2)-O(3) bond lengths are 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 C(1) atom. In the second H site, H(2) is bonded in a single-bond geometry to one C(2) atom. There are three inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Mn(1) and one C(1) 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. Linkers: 6 [O]C=O. Metal clusters: 2 [Mn]. RCSR code: pcu. The MOF has largest included sphere 3.69 A, density 1.58 g/cm3, surface area 3393.95 m2/g, accessible volume 0.26 cm3/g