Mg2C3PHO10 crystallizes in the triclinic P-1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(10), one O(3), one O(5), one O(7), and one O(9) atom to form MgO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra and  an edgeedge with one Mg(2)O5 square pyramid. The Mg(1)-O(1) bond length is 2.07 Å. The Mg(1)-O(10) bond length is 2.15 Å. The Mg(1)-O(3) bond length is 1.98 Å. The Mg(1)-O(5) bond length is 2.13 Å. The Mg(1)-O(7) bond length is 2.10 Å. The Mg(1)-O(9) bond length is 2.15 Å. In the second Mg site, Mg(2) is bonded to one O(1), one O(2), one O(6), one O(8), and one O(9) atom to form MgO5 square pyramids that share corners with two equivalent P(1)O4 tetrahedra and  an edgeedge with one Mg(1)O6 octahedra. The Mg(2)-O(1) bond length is 2.07 Å. The Mg(2)-O(2) bond length is 1.96 Å. The Mg(2)-O(6) bond length is 2.18 Å. The Mg(2)-O(8) bond length is 2.12 Å. The Mg(2)-O(9) bond length is 2.15 Å. There are three inequivalent C sites. In the first C site, C(1) is bonded in a distorted bent 120 degrees geometry to one O(5) and one O(6) atom. The C(1)-O(5) bond length is 1.25 Å. The C(1)-O(6) bond length is 1.25 Å. In the second C site, C(2) is bonded in a distorted bent 120 degrees geometry to one O(7) and one O(8) atom. The C(2)-O(7) bond length is 1.25 Å. The C(2)-O(8) bond length is 1.24 Å. In the third C site, C(3) is bonded in a distorted bent 120 degrees geometry to one O(10) and one O(9) atom. The C(3)-O(10) bond length is 1.23 Å. The C(3)-O(9) bond length is 1.26 Å. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra and corners with two equivalent Mg(2)O5 square pyramids. The corner-sharing octahedral tilt angles range from 37-52°. The P(1)-O(1) bond length is 1.54 Å. The P(1)-O(2) bond length is 1.50 Å. The P(1)-O(3) bond length is 1.51 Å. The P(1)-O(4) bond length is 1.59 Å. H(1) is bonded in a single-bond geometry to one O(4) atom. The H(1)-O(4) bond length is 0.82 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Mg(1), one Mg(2), and one P(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Mg(2) and one P(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Mg(1) and one P(1) atom. In the fourth O site, O(4) is bonded in a water-like geometry to one P(1) and one H(1) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Mg(1) and one C(1) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Mg(2) and one C(1) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one Mg(1) and one C(2) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Mg(2) and one C(2) atom. In the ninth O site, O(9) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one C(3) atom. In the tenth O site, O(10) is bonded in a bent 120 degrees geometry to one Mg(1) and one C(3) atom. Linkers: 2 [O]C(=O)C([O])=O. Metal clusters: 4 [Mg]. The MOF has largest included sphere 4.19 A, density 1.66 g/cm3, surface area 3233.20 m2/g, accessible volume 0.20 cm3/g