Mg3H4(C5O4)4 crystallizes in the orthorhombic Pbcn space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in an octahedral geometry to one O(1), one O(4), one O(5), one O(6), one O(7), and one O(8) atom. The Mg(1)-O(1) bond length is 2.03 Å. The Mg(1)-O(4) bond length is 2.02 Å. The Mg(1)-O(5) bond length is 2.10 Å. The Mg(1)-O(6) bond length is 2.13 Å. The Mg(1)-O(7) bond length is 2.11 Å. The Mg(1)-O(8) bond length is 2.09 Å. In the second Mg site, Mg(2) is bonded in an L-shaped geometry to two equivalent O(2) atoms. Both Mg(2)-O(2) bond lengths are 2.03 Å. There are ten inequivalent C sites. In the first C site, C(1) is bonded in a trigonal planar geometry to one C(2), one C(6), and one C(8) atom. The C(1)-C(2) bond length is 1.39 Å. The C(1)-C(6) bond length is 1.40 Å. The C(1)-C(8) bond length is 1.51 Å. In the second C site, C(2) is bonded in a distorted single-bond geometry to one C(1), one C(3), and one H(1) atom. The C(2)-C(3) bond length is 1.39 Å. The C(2)-H(1) bond length is 0.98 Å. In the third C site, C(3) is bonded in a trigonal planar geometry to one C(2), one C(4), and one C(9) atom. The C(3)-C(4) bond length is 1.40 Å. The C(3)-C(9) bond length is 1.52 Å. In the fourth C site, C(4) is bonded in a trigonal planar geometry to one C(10), one C(3), and one C(5) atom. The C(4)-C(10) bond length is 1.52 Å. The C(4)-C(5) bond length is 1.40 Å. In the fifth C site, C(5) is bonded in a distorted single-bond geometry to one C(4), one C(6), and one H(2) atom. The C(5)-C(6) bond length is 1.39 Å. The C(5)-H(2) bond length is 0.95 Å. In the sixth C site, C(6) is bonded in a trigonal planar geometry to one C(1), one C(5), and one C(7) atom. The C(6)-C(7) bond length is 1.52 Å. In the seventh C site, C(7) is bonded in a distorted bent 120 degrees geometry to one C(6), one O(7), and one O(8) atom. The C(7)-O(7) bond length is 1.25 Å. The C(7)-O(8) bond length is 1.26 Å. In the eighth C site, C(8) is bonded in a distorted bent 120 degrees geometry to one C(1), one O(1), and one O(2) atom. The C(8)-O(1) bond length is 1.25 Å. The C(8)-O(2) bond length is 1.25 Å. In the ninth C site, C(9) is bonded in a distorted bent 120 degrees geometry to one C(3), one O(3), and one O(4) atom. The C(9)-O(3) bond length is 1.24 Å. The C(9)-O(4) bond length is 1.25 Å. In the tenth C site, C(10) is bonded in a distorted bent 120 degrees geometry to one C(4), one O(5), and one O(6) atom. The C(10)-O(5) bond length is 1.25 Å. The C(10)-O(6) bond length is 1.25 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one C(2) atom. In the second H site, H(2) is bonded in a single-bond geometry to one C(5) atom. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Mg(1) and one C(8) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Mg(2) and one C(8) atom. In the third O site, O(3) is bonded in a single-bond geometry to one C(9) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Mg(1) and one C(9) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Mg(1) and one C(10) atom. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Mg(1) and one C(10) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Mg(1) and one C(7) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Mg(1) and one C(7) atom. Linkers: 8 [O]C(=O)c1cc(C([O])=O)c(C([O])=O)cc1C([O])=O. Metal clusters: 12 [Mg]. The MOF has largest included sphere 4.18 A, density 1.23 g/cm3, surface area 3992.59 m2/g, accessible volume 0.34 cm3/g