RbMn(HCO2)3 crystallizes in the monoclinic C2/c space group. Rb(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(3) atoms. Both Rb(1)-O(1) bond lengths are 2.95 Å. Both Rb(1)-O(2) bond lengths are 2.92 Å. There are two shorter (2.97 Å) and two longer (3.04 Å) Rb(1)-O(3) bond lengths. 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 2.18 Å. Both Mn(1)-O(2) bond lengths are 2.19 Å. Both Mn(1)-O(3) bond lengths are 2.18 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 1.11 Å. The C(1)-O(1) bond length is 1.27 Å. The C(1)-O(2) bond length is 1.27 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 1.11 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 3-coordinate geometry to one Rb(1), one Mn(1), and one C(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Rb(1), one Mn(1), and one C(1) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to two equivalent Rb(1), one Mn(1), and one C(2) atom. Linkers: 6 [O]C=O. Metal clusters: 2 [Rb] ,2 [Mn]. The MOF has largest included sphere 1.61 A, density 2.51 g/cm3, surface area 2554.29 m2/g, accessible volume 0.04 cm3/g