Co5H18(C17O9)2 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(2), one O(3), one O(5), and one O(9) atom to form distorted corner-sharing CoO5 square pyramids. The corner-sharing octahedral tilt angles are 60°. The Co(1)-O(1) bond length is 2.04 Å. The Co(1)-O(2) bond length is 2.29 Å. The Co(1)-O(3) bond length is 2.07 Å. The Co(1)-O(5) bond length is 2.02 Å. The Co(1)-O(9) bond length is 2.26 Å. In the second Co site, Co(2) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(6), one O(8), and one O(9) atom. The Co(2)-O(1) bond length is 2.12 Å. The Co(2)-O(6) bond length is 1.98 Å. The Co(2)-O(8) bond length is 2.07 Å. The Co(2)-O(9) bond length is 2.33 Å. In the third Co site, Co(3) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(7) atoms to form corner-sharing CoO6 octahedra. Both Co(3)-O(1) bond lengths are 2.09 Å. Both Co(3)-O(4) bond lengths are 2.14 Å. Both Co(3)-O(7) bond lengths are 2.11 Å. There are seventeen inequivalent C sites. In the first C site, C(1) is bonded in a trigonal planar geometry to one C(2), one C(6), and one C(7) atom. The C(1)-C(2) bond length is 1.38 Å. The C(1)-C(6) bond length is 1.39 Å. The C(1)-C(7) bond length is 1.52 Å. In the second C site, C(2) is bonded in a distorted single-bond geometry to one C(1), one C(3), and one H(1) atom. The C(2)-C(3) bond length is 1.43 Å. The C(2)-H(1) bond length is 0.93 Å. In the third C site, C(3) is bonded in a trigonal planar geometry to one C(2), one C(4), and one C(9) atom. The C(3)-C(4) bond length is 1.38 Å. The C(3)-C(9) bond length is 1.53 Å. In the fourth C site, C(4) is bonded in a distorted single-bond geometry to one C(3), one C(5), and one H(2) atom. The C(4)-C(5) bond length is 1.42 Å. 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(4), one C(6), and one C(8) atom. The C(5)-C(6) bond length is 1.37 Å. The C(5)-C(8) bond length is 1.51 Å. In the sixth C site, C(6) is bonded in a distorted single-bond geometry to one C(1), one C(5), and one H(3) atom. The C(6)-H(3) bond length is 0.93 Å. In the seventh C site, C(7) is bonded in a distorted bent 120 degrees geometry to one C(1), one O(2), and one O(3) atom. The C(7)-O(2) bond length is 1.26 Å. The C(7)-O(3) bond length is 1.29 Å. In the eighth C site, C(8) is bonded in a distorted bent 120 degrees geometry to one C(5), one O(4), and one O(5) atom. The C(8)-O(4) bond length is 1.25 Å. The C(8)-O(5) bond length is 1.26 Å. In the ninth C site, C(9) is bonded in a water-like geometry to one C(10); one C(3); and two equivalent H(4,5) atoms. The C(9)-C(10) bond length is 1.50 Å. Both C(9)-H(4,5) bond lengths are 0.97 Å. In the tenth C site, C(10) is bonded in a trigonal planar geometry to one C(11), one C(15), and one C(9) atom. The C(10)-C(11) bond length is 1.37 Å. The C(10)-C(15) bond length is 1.42 Å. In the eleventh C site, C(11) is bonded in a distorted single-bond geometry to one C(10), one C(12), and one H(6) atom. The C(11)-C(12) bond length is 1.41 Å. The C(11)-H(6) bond length is 0.93 Å. In the twelfth C site, C(12) is bonded in a trigonal planar geometry to one C(11), one C(13), and one C(16) atom. The C(12)-C(13) bond length is 1.36 Å. The C(12)-C(16) bond length is 1.50 Å. In the thirteenth C site, C(13) is bonded in a distorted single-bond geometry to one C(12), one C(14), and one H(7) atom. The C(13)-C(14) bond length is 1.39 Å. The C(13)-H(7) bond length is 0.93 Å. In the fourteenth C site, C(14) is bonded in a trigonal planar geometry to one C(13), one C(15), and one C(17) atom. The C(14)-C(15) bond length is 1.39 Å. The C(14)-C(17) bond length is 1.50 Å. In the fifteenth C site, C(15) is bonded in a distorted single-bond geometry to one C(10), one C(14), and one H(8) atom. The C(15)-H(8) bond length is 0.93 Å. In the sixteenth C site, C(16) is bonded in a distorted bent 120 degrees geometry to one C(12), one O(6), and one O(7) atom. The C(16)-O(6) bond length is 1.25 Å. The C(16)-O(7) bond length is 1.27 Å. In the seventeenth C site, C(17) is bonded in a distorted bent 120 degrees geometry to one C(14), one O(8), and one O(9) atom. The C(17)-O(8) bond length is 1.24 Å. The C(17)-O(9) bond length is 1.26 Å. There are eight inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one C(2) 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. In the fourth H site, H(4,5) is bonded in a single-bond geometry to one C(9) atom. In the fifth H site, H(6) is bonded in a single-bond geometry to one C(11) atom. In the sixth H site, H(7) is bonded in a single-bond geometry to one C(13) atom. In the seventh H site, H(8) is bonded in a single-bond geometry to one C(15) atom. In the eighth H site, H(9) is bonded in a single-bond geometry to one O(1) atom. The H(9)-O(1) bond length is 0.98 Å. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Co(1), one Co(2), one Co(3), and one H(9) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Co(1) and one C(7) atom. In the third O site, O(3) is bonded in an L-shaped geometry to one Co(1) and one C(7) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Co(3) and one C(8) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Co(1) and one C(8) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Co(2) and one C(16) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one Co(3) and one C(16) atom. In the eighth O site, O(8) is bonded in a distorted L-shaped geometry to one Co(2) and one C(17) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Co(1), one Co(2), and one C(17) atom. Linkers: 4 [O]C(=O)c1cc(Cc2cc(C([O])=O)cc(C([O])=O)c2)cc(C([O])=O)c1. Metal clusters: 2 O[Co]12(O[C]O[Co]O[C]O[Co]3(O[C]O[Co]O[C]O[Co]4(O)(O[C]O3)O[C]O4)O[C]O1)O[C]O2. RCSR code: scu. The MOF has largest included sphere 3.86 A, density 1.59 g/cm3, surface area 3356.65 m2/g, accessible volume 0.23 cm3/g