Al4P7(HO3)7 crystallizes in the trigonal P-3c1 space group. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(4), one O(5), one O(6), and one O(7) atom to form AlO5 square pyramids that share  a cornercorner with one P(1)HO3 tetrahedra,  a cornercorner with one P(3)HO3 tetrahedra, and corners with three equivalent P(2)HO3 tetrahedra. The Al(1)-O(1) bond length is 1.90 Å. The Al(1)-O(4) bond length is 1.86 Å. The Al(1)-O(5) bond length is 1.87 Å. The Al(1)-O(6) bond length is 1.87 Å. The Al(1)-O(7) bond length is 1.87 Å. In the second Al site, Al(2) is bonded to six equivalent O(3) atoms to form AlO6 octahedra that share corners with six equivalent P(1)HO3 tetrahedra. All Al(2)-O(3) bond lengths are 1.90 Å. In the third Al site, Al(3) is bonded to six equivalent O(2) atoms to form AlO6 octahedra that share corners with six equivalent P(1)HO3 tetrahedra. All Al(3)-O(2) bond lengths are 1.90 Å. There are three inequivalent P sites. In the first P site, P(3) is bonded to one H(3) and three equivalent O(7) atoms to form distorted PHO3 tetrahedra that share corners with three equivalent Al(1)O5 square pyramids. The P(3)-H(3) bond length is 1.43 Å. All P(3)-O(7) bond lengths are 1.52 Å. In the second P site, 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 Al(2)O6 octahedra,  a cornercorner with one Al(3)O6 octahedra, and  a cornercorner with one Al(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 40-48°. The P(1)-H(1) bond length is 1.25 Å. The P(1)-O(1) bond length is 1.52 Å. The P(1)-O(2) bond length is 1.52 Å. The P(1)-O(3) bond length is 1.52 Å. In the third P site, P(2) is bonded to one H(2), one O(4), one O(5), and one O(6) atom to form distorted PHO3 tetrahedra that share corners with three equivalent Al(1)O5 square pyramids. The P(2)-H(2) bond length is 1.46 Å. The P(2)-O(4) bond length is 1.52 Å. The P(2)-O(5) bond length is 1.52 Å. The P(2)-O(6) bond length is 1.50 Å. There are three inequivalent H sites. In the first H site, H(3) is bonded in a single-bond geometry to one P(3) atom. In the second H site, H(1) is bonded in a single-bond geometry to one P(1) atom. In the third H site, H(2) is bonded in a single-bond geometry to one P(2) atom. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Al(1) and one P(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Al(3) and one P(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Al(2) and one P(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Al(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Al(1) and one P(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Al(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Al(1) and one P(3) atom. Linkers: 28 [O][PH]([O])=O. Metal clusters: 16 [Al]. The MOF has largest included sphere 4.83 A, density 1.70 g/cm3, surface area 2958.76 m2/g, accessible volume 0.23 cm3/g