V9(P2O9)4 crystallizes in the monoclinic P2_1/c space group. There are five inequivalent V sites. In the first V site, V(1) is bonded in a distorted see-saw-like geometry to one O(13), one O(15), one O(4), and one O(9) atom. The V(1)-O(13) bond length is 1.97 Å. The V(1)-O(15) bond length is 1.98 Å. The V(1)-O(4) bond length is 1.95 Å. The V(1)-O(9) bond length is 1.94 Å. In the second V site, V(2) is bonded in a 4-coordinate geometry to one O(1), one O(14), one O(15), and one O(16) atom. The V(2)-O(1) bond length is 1.96 Å. The V(2)-O(14) bond length is 1.95 Å. The V(2)-O(15) bond length is 2.00 Å. The V(2)-O(16) bond length is 1.96 Å. In the third V site, V(3) is bonded in a distorted see-saw-like geometry to one O(10), one O(11), one O(12), and one O(17) atom. The V(3)-O(10) bond length is 1.96 Å. The V(3)-O(11) bond length is 1.98 Å. The V(3)-O(12) bond length is 1.99 Å. The V(3)-O(17) bond length is 1.97 Å. In the fourth V site, V(4) is bonded in a 4-coordinate geometry to one O(12), one O(18), one O(6), and one O(7) atom. The V(4)-O(12) bond length is 1.98 Å. The V(4)-O(18) bond length is 2.00 Å. The V(4)-O(6) bond length is 1.95 Å. The V(4)-O(7) bond length is 1.96 Å. In the fifth V site, V(5) is bonded in a square co-planar geometry to two equivalent O(5) and two equivalent O(8) atoms. Both V(5)-O(5) bond lengths are 1.99 Å. Both V(5)-O(8) bond lengths are 1.99 Å. There are four inequivalent P sites. In the first P site, P(1) is bonded in a tetrahedral geometry to one O(10), one O(17), one O(3), and one O(7) atom. The P(1)-O(10) bond length is 1.54 Å. The P(1)-O(17) bond length is 1.53 Å. The P(1)-O(3) bond length is 1.54 Å. The P(1)-O(7) bond length is 1.52 Å. In the second P site, P(2) is bonded in a tetrahedral geometry to one O(1), one O(11), one O(18), and one O(5) atom. The P(2)-O(1) bond length is 1.53 Å. The P(2)-O(11) bond length is 1.53 Å. The P(2)-O(18) bond length is 1.53 Å. The P(2)-O(5) bond length is 1.52 Å. In the third P site, P(3) is bonded in a tetrahedral geometry to one O(13), one O(16), one O(2), and one O(4) atom. The P(3)-O(13) bond length is 1.51 Å. The P(3)-O(16) bond length is 1.52 Å. The P(3)-O(2) bond length is 1.54 Å. The P(3)-O(4) bond length is 1.53 Å. In the fourth P site, P(4) is bonded in a tetrahedral geometry to one O(14), one O(6), one O(8), and one O(9) atom. The P(4)-O(14) bond length is 1.53 Å. The P(4)-O(6) bond length is 1.51 Å. The P(4)-O(8) bond length is 1.54 Å. The P(4)-O(9) bond length is 1.52 Å. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one V(2) and one P(2) atom. In the second O site, O(2) is bonded in a single-bond geometry to one P(3) atom. In the third O site, O(3) is bonded in a single-bond geometry to one P(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one V(1) and one P(3) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one V(5) and one P(2) atom. In the sixth O site, O(6) is bonded in a single-bond geometry to one V(4) and one P(4) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one V(4) and one P(1) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one V(5) and one P(4) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one V(1) and one P(4) atom. In the tenth O site, O(10) is bonded in a distorted bent 120 degrees geometry to one V(3) and one P(1) atom. In the eleventh O site, O(11) is bonded in a distorted bent 150 degrees geometry to one V(3) and one P(2) atom. In the twelfth O site, O(12) is bonded in a bent 120 degrees geometry to one V(3) and one V(4) atom. In the thirteenth O site, O(13) is bonded in a single-bond geometry to one V(1) and one P(3) atom. In the fourteenth O site, O(14) is bonded in a distorted bent 120 degrees geometry to one V(2) and one P(4) atom. In the fifteenth O site, O(15) is bonded in a distorted bent 150 degrees geometry to one V(1) and one V(2) atom. In the sixteenth O site, O(16) is bonded in a bent 120 degrees geometry to one V(2) and one P(3) atom. In the seventeenth O site, O(17) is bonded in a distorted bent 150 degrees geometry to one V(3) and one P(1) atom. In the eighteenth O site, O(18) is bonded in a distorted bent 120 degrees geometry to one V(4) and one P(2) atom. Linkers: 16 [O]P([O])([O])=O. Metal clusters: 18 [V]. The MOF has largest included sphere 6.32 A, density 1.60 g/cm3, surface area 2569.87 m2/g, accessible volume 0.28 cm3/g