YC2O5 crystallizes in the orthorhombic C222_1 space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. Both Y(1)-O(1) bond lengths are 2.42 Å. Both Y(1)-O(3) bond lengths are 2.41 Å. Both Y(1)-O(4) bond lengths are 2.38 Å. Both Y(1)-O(5) bond lengths are 2.47 Å. In the second Y site, Y(2) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. Both Y(2)-O(2) bond lengths are 2.31 Å. Both Y(2)-O(3) bond lengths are 2.47 Å. Both Y(2)-O(4) bond lengths are 2.47 Å. Both Y(2)-O(5) bond lengths are 2.32 Å. There are two inequivalent C sites. In the first C site, C(1) is bonded in a distorted bent 120 degrees geometry to one O(1) and one O(2) atom. The C(1)-O(1) bond length is 1.29 Å. The C(1)-O(2) bond length is 1.26 Å. In the second C site, C(2) is bonded in a trigonal planar geometry to one O(3), one O(4), and one O(5) atom. The C(2)-O(3) bond length is 1.31 Å. The C(2)-O(4) bond length is 1.26 Å. The C(2)-O(5) bond length is 1.30 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Y(1) and one C(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Y(2) and one C(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Y(1), one Y(2), and one C(2) atom. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Y(1), one Y(2), and one C(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Y(1), one Y(2), and one C(2) atom. Linkers: 2 [O]C(=O)C([O])=O. Metal clusters: 4 [Y]. The MOF has largest included sphere 4.15 A, density 2.31 g/cm3, surface area 2048.98 m2/g, accessible volume 0.13 cm3/g