FeP2(HO3)2 crystallizes in the trigonal R-3 space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form FeO6 octahedra that share corners with six equivalent P(1)HO3 tetrahedra. All Fe(1)-O(2) bond lengths are 2.02 Å. All Fe(1)-O(3) bond lengths are 2.00 Å. In the second Fe site, Fe(2) is bonded to six equivalent O(1) atoms to form FeO6 octahedra that share corners with six equivalent P(1)HO3 tetrahedra. All Fe(2)-O(1) bond lengths are 2.01 Å. P(1) is bonded to one H(1), one O(1), one O(2), and one O(3) atom to form PHO3 tetrahedra that share  a cornercorner with one Fe(2)O6 octahedra and corners with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 43-56°. The P(1)-H(1) bond length is 1.17 Å. The P(1)-O(1) bond length is 1.53 Å. The P(1)-O(2) bond length is 1.53 Å. The P(1)-O(3) bond length is 1.53 Å. H(1) is bonded in a single-bond geometry to one P(1) atom. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Fe(2) and one P(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Fe(1) and one P(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Fe(1) and one P(1) atom. Linkers: 18 [O][PH]([O])=O. Metal clusters: 9 [Fe]. The MOF has largest included sphere 4.75 A, density 1.90 g/cm3, surface area 2637.46 m2/g, accessible volume 0.24 cm3/g