Co5C18P3H9O18Cl crystallizes in the trigonal P-3c1 space group. There are three inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form CoO4 tetrahedra that share  a cornercorner with one Co(2)O6 octahedra and corners with three equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 73°. The Co(1)-O(1) bond length is 1.99 Å. The Co(1)-O(3) bond length is 1.96 Å. The Co(1)-O(4) bond length is 1.93 Å. The Co(1)-O(5) bond length is 1.94 Å. In the second Co site, Co(2) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form CoO6 octahedra that share corners with three equivalent Co(1)O4 tetrahedra and corners with three equivalent P(1)O4 tetrahedra. All Co(2)-O(1) bond lengths are 2.11 Å. All Co(2)-O(2) bond lengths are 2.11 Å. In the third Co site, Co(3) is bonded to three equivalent O(6) and one Cl(1) atom to form CoClO3 tetrahedra that share corners with three equivalent P(1)O4 tetrahedra. All Co(3)-O(6) bond lengths are 1.93 Å. The Co(3)-Cl(1) bond length is 2.30 Å. There are six inequivalent C sites. In the first C site, C(1) is bonded in a trigonal planar geometry to one C(2), one C(3), and one C(4) atom. The C(1)-C(2) bond length is 1.50 Å. The C(1)-C(3) bond length is 1.36 Å. The C(1)-C(4) bond length is 1.42 Å. In the second C site, C(2) is bonded in a distorted bent 120 degrees geometry to one C(1), one O(2), and one O(3) atom. The C(2)-O(2) bond length is 1.25 Å. The C(2)-O(3) bond length is 1.26 Å. In the third C site, C(3) is bonded in a distorted single-bond geometry to one C(1), one C(5), and one H(1) atom. The C(3)-C(5) bond length is 1.41 Å. The C(3)-H(1) bond length is 0.93 Å. In the fourth C site, C(4) is bonded in a distorted single-bond geometry to one C(1) and one H(2) atom. The C(4)-H(2) bond length is 0.93 Å. In the fifth C site, C(5) is bonded in a trigonal planar geometry to one C(3), one C(5), and one C(6) atom. The C(5)-C(5) bond length is 1.42 Å. The C(5)-C(6) bond length is 1.42 Å. In the sixth C site, C(6) is bonded in a distorted single-bond geometry to one C(5) and one H(3) atom. The C(6)-H(3) bond length is 0.93 Å. P(1) is bonded to one O(1), one O(4), one O(5), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one Co(2)O6 octahedra,  a cornercorner with one Co(3)ClO3 tetrahedra, and corners with three equivalent Co(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 45°. The P(1)-O(1) bond length is 1.55 Å. The P(1)-O(4) bond length is 1.52 Å. The P(1)-O(5) bond length is 1.53 Å. The P(1)-O(6) bond length is 1.52 Å. There are three 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 single-bond geometry to one C(6) atom. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(2), and one P(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Co(2) and one C(2) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Co(1) and one C(2) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Co(1) and one P(1) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Co(1) and one P(1) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Co(3) and one P(1) atom. Cl(1) is bonded in a single-bond geometry to one Co(3) atom. Linkers: 6 [O]C(=O)c1ccc2cc(C([O])=O)ccc2c1. Metal clusters: 20 [Co]. The MOF has largest included sphere 8.36 A, density 1.26 g/cm3, surface area 2902.34 m2/g, accessible volume 0.38 cm3/g