Mn(HCOO)2 crystallizes in the orthorhombic Pbcn space group. Mn(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form edge-sharing MnO6 octahedra. Both Mn(1)-O(2) bond lengths are 2.14 Å. There are two shorter (2.21 Å) and two longer (2.25 Å) Mn(1)-O(1) bond lengths. 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. H(1) is bonded in a single-bond geometry to one C(1) atom. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent 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. Linkers: 8 [O]C=O. Metal clusters: 4 [Mn]. The MOF has largest included sphere 2.04 A, density 2.33 g/cm3, surface area 2176.59 m2/g, accessible volume 0.08 cm3/g