Mg(HCOO)2 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles range from 64-66°. The Mg(1)-O(1) bond length is 2.10 Å. The Mg(1)-O(2) bond length is 2.12 Å. The Mg(1)-O(3) bond length is 2.11 Å. The Mg(1)-O(4) bond length is 2.09 Å. The Mg(1)-O(5) bond length is 2.11 Å. The Mg(1)-O(6) bond length is 2.07 Å. In the second Mg site, Mg(2) is bonded to two equivalent O(6), two equivalent O(7), and two equivalent O(8) atoms to form corner-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 64°. Both Mg(2)-O(6) bond lengths are 2.14 Å. Both Mg(2)-O(7) bond lengths are 2.07 Å. Both Mg(2)-O(8) bond lengths are 2.06 Å. In the third Mg site, Mg(3) is bonded to one O(1), one O(12), one O(2), one O(3), one O(5), and one O(9) atom to form edge-sharing MgO6 octahedra. The Mg(3)-O(1) bond length is 2.07 Å. The Mg(3)-O(12) bond length is 2.05 Å. The Mg(3)-O(2) bond length is 2.10 Å. The Mg(3)-O(3) bond length is 2.11 Å. The Mg(3)-O(5) bond length is 2.13 Å. The Mg(3)-O(9) bond length is 2.03 Å. In the fourth Mg site, Mg(4) is bonded to two equivalent O(10), two equivalent O(11), and two equivalent O(4) atoms to form corner-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 66°. Both Mg(4)-O(10) bond lengths are 2.07 Å. Both Mg(4)-O(11) bond lengths are 2.05 Å. Both Mg(4)-O(4) bond lengths are 2.13 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(7) atom. The C(1)-H(1) bond length is 1.11 Å. The C(1)-O(1) bond length is 1.29 Å. The C(1)-O(7) 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(2), and one O(8) atom. The C(2)-H(2) bond length is 1.11 Å. The C(2)-O(2) bond length is 1.29 Å. The C(2)-O(8) bond length is 1.25 Å. In the third C site, C(3) is bonded in a trigonal planar geometry to one H(3), one O(12), and one O(3) atom. The C(3)-H(3) bond length is 1.10 Å. The C(3)-O(12) bond length is 1.26 Å. The C(3)-O(3) bond length is 1.29 Å. In the fourth C site, C(4) is bonded in a trigonal planar geometry to one H(4), one O(4), and one O(9) atom. The C(4)-H(4) bond length is 1.10 Å. The C(4)-O(4) bond length is 1.29 Å. The C(4)-O(9) bond length is 1.25 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(5) 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(5) 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(6) atom. The C(6)-H(6) bond length is 1.10 Å. The C(6)-O(11) bond length is 1.25 Å. The C(6)-O(6) bond length is 1.29 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 Mg(1), one Mg(3), and one C(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(3), and one C(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(3), and one C(3) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Mg(1), one Mg(4), and one C(4) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(3), and one C(5) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Mg(1), one Mg(2), and one C(6) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Mg(2) and one C(1) atom. In the eighth O site, O(8) is bonded in a distorted bent 120 degrees geometry to one Mg(2) and one C(2) atom. In the ninth O site, O(9) is bonded in a bent 120 degrees geometry to one Mg(3) and one C(4) atom. In the tenth O site, O(10) is bonded in a distorted bent 120 degrees geometry to one Mg(4) and one C(5) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one Mg(4) and one C(6) atom. In the twelfth O site, O(12) is bonded in a bent 120 degrees geometry to one Mg(3) and one C(3) atom. Linkers: 24 [O]C=O. Metal clusters: 12 [Mg]. The MOF has largest included sphere 4.73 A, density 1.38 g/cm3, surface area 3658.01 m2/g, accessible volume 0.26 cm3/g