MgH8(C7O3)2 crystallizes in the trigonal P3_221 space group. Mg(1) is bonded in a rectangular see-saw-like geometry to two equivalent O(1) and two equivalent O(3) atoms. Both Mg(1)-O(1) bond lengths are 2.12 Å. Both Mg(1)-O(3) bond lengths are 2.02 Å. There are seven inequivalent C sites. In the first C site, C(4) is bonded in a distorted single-bond geometry to one C(1), one C(3), and one H(2) atom. The C(4)-C(1) bond length is 1.39 Å. The C(4)-C(3) bond length is 1.39 Å. The C(4)-H(2) bond length is 0.95 Å. In the second C site, C(5) is bonded in a distorted bent 120 degrees geometry to one C(7), one O(2), and one O(3) atom. The C(5)-C(7) bond length is 1.49 Å. The C(5)-O(2) bond length is 1.28 Å. The C(5)-O(3) bond length is 1.25 Å. In the third C site, C(6) is bonded in a distorted single-bond geometry to one C(1), one C(2), and one O(1) atom. The C(6)-C(1) bond length is 1.41 Å. The C(6)-C(2) bond length is 1.38 Å. The C(6)-O(1) bond length is 1.38 Å. In the fourth C site, C(7) is bonded in a trigonal planar geometry to one C(2), one C(3), and one C(5) atom. The C(7)-C(2) bond length is 1.39 Å. The C(7)-C(3) bond length is 1.36 Å. In the fifth C site, C(1) is bonded in a trigonal planar geometry to one C(1), one C(4), and one C(6) atom. The C(1)-C(1) bond length is 1.46 Å. In the sixth C site, C(2) is bonded in a distorted trigonal planar geometry to one C(6), one C(7), and one H(4) atom. The C(2)-H(4) bond length is 0.95 Å. In the seventh C site, C(3) is bonded in a distorted trigonal planar geometry to one C(4), one C(7), and one H(1) atom. The C(3)-H(1) bond length is 0.95 Å. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one C(3) atom. In the second H site, H(2) is bonded in a single-bond geometry to one C(4) atom. In the third H site, H(3) is bonded in a distorted linear geometry to one O(1) and one O(2) atom. The H(3)-O(1) bond length is 1.04 Å. The H(3)-O(2) bond length is 1.44 Å. In the fourth H site, H(4) 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 Mg(1), one C(6), and one H(3) atom. In the second O site, O(2) is bonded in a water-like geometry to one C(5) and one H(3) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Mg(1) and one C(5) atom. Linkers: 1 [O]C(=O)c1ccc(-c2ccc(C(=O)O[Mg]OC(=O)c3ccc(-c4ccc(C([O])=O)cc4O)c(O)c3)cc2O)c(O)c1.[O]C(=O)c1ccc(-c2ccc(C([O])=O)cc2O)c(O)c1. Metal clusters: 2 O=[C]O[Mg]O[C]=O.[OH].[OH]. RCSR code: tsx. The MOF has largest included sphere 6.52 A, density 0.65 g/cm3, surface area 4700.06 m2/g, accessible volume 1.04 cm3/g