Mg2H9(C3O)8 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted T-shaped geometry to one O(1), one O(5), and one O(7) atom. The Mg(1)-O(1) bond length is 2.07 Å. The Mg(1)-O(5) bond length is 1.96 Å. The Mg(1)-O(7) bond length is 1.97 Å. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(4), one O(6), and one O(8) atom. The Mg(2)-O(1) bond length is 2.46 Å. The Mg(2)-O(3) bond length is 2.00 Å. The Mg(2)-O(4) bond length is 2.07 Å. The Mg(2)-O(6) bond length is 1.97 Å. The Mg(2)-O(8) bond length is 1.97 Å. There are twenty-four inequivalent C sites. In the first C site, C(1) is bonded in a distorted bent 120 degrees geometry to one C(14), one O(2), and one O(8) atom. The C(1)-C(14) bond length is 1.51 Å. The C(1)-O(2) bond length is 1.25 Å. The C(1)-O(8) bond length is 1.23 Å. In the second C site, C(2) is bonded in a single-bond geometry to one C(9) and one H(3) atom. The C(2)-C(9) bond length is 1.44 Å. The C(2)-H(3) bond length is 0.93 Å. In the third C site, C(3) is bonded in a distorted bent 120 degrees geometry to one C(10), one O(6), and one O(7) atom. The C(3)-C(10) bond length is 1.51 Å. The C(3)-O(6) bond length is 1.22 Å. The C(3)-O(7) bond length is 1.27 Å. In the fourth C site, C(4) is bonded in a distorted single-bond geometry to one C(16), one C(19), and one H(5) atom. The C(4)-C(16) bond length is 1.38 Å. The C(4)-C(19) bond length is 1.38 Å. The C(4)-H(5) bond length is 0.93 Å. In the fifth C site, C(5) is bonded in a single-bond geometry to one C(11) and one H(9) atom. The C(5)-C(11) bond length is 1.43 Å. The C(5)-H(9) bond length is 0.93 Å. In the sixth C site, C(6) is bonded in a distorted single-bond geometry to one C(10), one C(17), and one H(4) atom. The C(6)-C(10) bond length is 1.40 Å. The C(6)-C(17) bond length is 1.39 Å. The C(6)-H(4) bond length is 0.93 Å. In the seventh C site, C(7) is bonded in a trigonal planar geometry to one C(19), one C(22), and one C(9) atom. The C(7)-C(19) bond length is 1.47 Å. The C(7)-C(22) bond length is 1.38 Å. The C(7)-C(9) bond length is 1.40 Å. In the eighth C site, C(8) is bonded in a trigonal planar geometry to one C(20), one C(23), and one C(24) atom. The C(8)-C(20) bond length is 1.37 Å. The C(8)-C(23) bond length is 1.40 Å. The C(8)-C(24) bond length is 1.50 Å. In the ninth C site, C(9) is bonded in a trigonal planar geometry to one C(2), one C(21), and one C(7) atom. The C(9)-C(21) bond length is 1.43 Å. In the tenth C site, C(10) is bonded in a trigonal planar geometry to one C(23), one C(3), and one C(6) atom. The C(10)-C(23) bond length is 1.39 Å. In the eleventh C site, C(11) is bonded in a trigonal planar geometry to one C(18), one C(21), and one C(5) atom. The C(11)-C(18) bond length is 1.41 Å. The C(11)-C(21) bond length is 1.43 Å. In the twelfth C site, C(12) is bonded in a distorted single-bond geometry to one C(14), one C(16), and one H(1) atom. The C(12)-C(14) bond length is 1.38 Å. The C(12)-C(16) bond length is 1.39 Å. The C(12)-H(1) bond length is 0.93 Å. In the thirteenth C site, C(13) is bonded in a bent 120 degrees geometry to one C(16), one O(3), and one O(5) atom. The C(13)-C(16) bond length is 1.50 Å. The C(13)-O(3) bond length is 1.25 Å. The C(13)-O(5) bond length is 1.25 Å. In the fourteenth C site, C(14) is bonded in a trigonal planar geometry to one C(1), one C(12), and one C(15) atom. The C(14)-C(15) bond length is 1.39 Å. In the fifteenth C site, C(15) is bonded in a distorted single-bond geometry to one C(14), one C(19), and one H(7) atom. The C(15)-C(19) bond length is 1.40 Å. The C(15)-H(7) bond length is 0.93 Å. In the sixteenth C site, C(16) is bonded in a trigonal planar geometry to one C(12), one C(13), and one C(4) atom. In the seventeenth C site, C(17) is bonded in a trigonal planar geometry to one C(18), one C(20), and one C(6) atom. The C(17)-C(18) bond length is 1.48 Å. The C(17)-C(20) bond length is 1.39 Å. In the eighteenth C site, C(18) is bonded in a trigonal planar geometry to one C(11), one C(17), and one C(22) atom. The C(18)-C(22) bond length is 1.40 Å. In the nineteenth C site, C(19) is bonded in a trigonal planar geometry to one C(15), one C(4), and one C(7) atom. In the twentieth C site, C(20) is bonded in a distorted single-bond geometry to one C(17), one C(8), and one H(2) atom. The C(20)-H(2) bond length is 0.93 Å. In the twenty-first C site, C(21) is bonded in a trigonal planar geometry to one C(11), one C(21), and one C(9) atom. The C(21)-C(21) bond length is 1.43 Å. In the twenty-second C site, C(22) is bonded in a single-bond geometry to one C(18), one C(7), and one H(6) atom. The C(22)-H(6) bond length is 0.93 Å. In the twenty-third C site, C(23) is bonded in a distorted trigonal planar geometry to one C(10), one C(8), and one H(8) atom. The C(23)-H(8) bond length is 0.93 Å. In the twenty-fourth C site, C(24) is bonded in a distorted bent 120 degrees geometry to one C(8), one O(1), and one O(4) atom. The C(24)-O(1) bond length is 1.25 Å. The C(24)-O(4) bond length is 1.26 Å. There are nine inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one C(12) atom. In the second H site, H(2) is bonded in a single-bond geometry to one C(20) atom. In the third H site, H(3) is bonded in a single-bond geometry to one C(2) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one C(6) atom. In the fifth H site, H(5) is bonded in a single-bond geometry to one C(4) atom. In the sixth H site, H(6) is bonded in a single-bond geometry to one C(22) atom. In the seventh H site, H(7) is bonded in a single-bond geometry to one C(15) atom. In the eighth H site, H(8) is bonded in a single-bond geometry to one C(23) atom. In the ninth H site, H(9) 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 3-coordinate geometry to one Mg(1), one Mg(2), and one C(24) atom. In the second O site, O(2) is bonded in a single-bond geometry to one C(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Mg(2) and one C(13) atom. In the fourth O site, O(4) is bonded in a water-like geometry to one Mg(2) and one C(24) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Mg(1) and one C(13) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Mg(2) and one C(3) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Mg(1) and one C(3) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Mg(2) and one C(1) atom. Linkers: 1 [O]C(=O)c1cc([C]=O)cc(-c2cc(-c3cc(C([O])=O)cc(C([O])=O)c3)c3ccc4c(-c5cc(C([O])=O)cc(C([O])=O)c5)cc(-c5cc(C([O])=O)cc(C([O])=O)c5)c5ccc2c3c54)c1 ,1 [O]C(=O)c1cc(C([O])=O)cc(-c2cc(-c3cc(C([O])=O)cc(C([O])=O)c3)c3ccc4c(-c5cc(C([O])=O)cc(C([O])=O)c5)cc(-c5cc(C([O])=O)cc(C([O])=O)c5)c5ccc2c3c54)c1. Metal clusters: 4 O=[C]O[Mg]O[C]O[Mg]O[C]=O.[O][C]=O. The MOF has largest included sphere 6.43 A, density 0.76 g/cm3, surface area 4328.82 m2/g, accessible volume 0.85 cm3/g