Fe(HCOO)2 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(11), one O(3), one O(5), one O(7), and one O(9) atom to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 65-67°. The Fe(1)-O(1) bond length is 2.08 Å. The Fe(1)-O(11) bond length is 2.10 Å. The Fe(1)-O(3) bond length is 2.16 Å. The Fe(1)-O(5) bond length is 2.10 Å. The Fe(1)-O(7) bond length is 2.13 Å. The Fe(1)-O(9) bond length is 2.17 Å. In the second Fe site, Fe(2) is bonded to one O(11), one O(4), one O(5), one O(6), one O(7), and one O(9) atom to form edge-sharing FeO6 octahedra. The Fe(2)-O(11) bond length is 2.12 Å. The Fe(2)-O(4) bond length is 2.06 Å. The Fe(2)-O(5) bond length is 2.15 Å. The Fe(2)-O(6) bond length is 2.09 Å. The Fe(2)-O(7) bond length is 2.14 Å. The Fe(2)-O(9) bond length is 2.10 Å. In the third Fe site, Fe(3) is bonded to two equivalent O(1), two equivalent O(12), and two equivalent O(8) atoms to form corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 67°. Both Fe(3)-O(1) bond lengths are 2.21 Å. Both Fe(3)-O(12) bond lengths are 2.09 Å. Both Fe(3)-O(8) bond lengths are 2.08 Å. In the fourth Fe site, Fe(4) is bonded to two equivalent O(10), two equivalent O(2), and two equivalent O(3) atoms to form corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 65°. Both Fe(4)-O(10) bond lengths are 2.09 Å. Both Fe(4)-O(2) bond lengths are 2.07 Å. Both Fe(4)-O(3) bond lengths are 2.14 Å. There are six 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 1.29 Å. The C(1)-O(2) bond length is 1.25 Å. In the second 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 1.10 Å. The C(2)-O(3) bond length is 1.29 Å. The C(2)-O(4) bond length is 1.26 Å. In the third C site, C(3) is bonded in a trigonal planar geometry to one H(3), one O(5), and one O(6) atom. The C(3)-H(3) bond length is 1.10 Å. The C(3)-O(5) bond length is 1.29 Å. The C(3)-O(6) bond length is 1.26 Å. In the fourth C site, C(4) is bonded in a trigonal planar geometry to one H(4), one O(7), and one O(8) atom. The C(4)-H(4) bond length is 1.11 Å. The C(4)-O(7) bond length is 1.28 Å. The C(4)-O(8) bond length is 1.26 Å. In the fifth C site, C(5) is bonded in a trigonal planar geometry to one H(5), one O(10), and one O(9) atom. The C(5)-H(5) bond length is 1.11 Å. The C(5)-O(10) bond length is 1.25 Å. The C(5)-O(9) bond length is 1.29 Å. In the sixth C site, C(6) is bonded in a trigonal planar geometry to one H(6), one O(11), and one O(12) atom. The C(6)-H(6) bond length is 1.11 Å. The C(6)-O(11) bond length is 1.29 Å. The C(6)-O(12) bond length is 1.26 Å. There are six 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 single-bond geometry to one C(3) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one C(4) atom. In the fifth H site, H(5) is bonded in a single-bond geometry to one C(5) atom. In the sixth H site, H(6) is bonded in a single-bond geometry to one C(6) atom. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(3), and one C(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Fe(4) and one C(1) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to one Fe(1), one Fe(4), and one C(2) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Fe(2) and one C(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one C(3) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Fe(2) and one C(3) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(2), and one C(4) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Fe(3) and one C(4) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(2), and one C(5) atom. In the tenth O site, O(10) is bonded in a distorted bent 120 degrees geometry to one Fe(4) and one C(5) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(2), and one C(6) atom. In the twelfth O site, O(12) is bonded in a distorted bent 120 degrees geometry to one Fe(3) and one C(6) atom. Linkers: 24 [O]C=O. Metal clusters: 12 [Fe]. The MOF has largest included sphere 4.60 A, density 1.81 g/cm3, surface area 2597.46 m2/g, accessible volume 0.18 cm3/g