YH2(CO3)2 crystallizes in the orthorhombic Cmcm space group. Y(1) is bonded in a 9-coordinate geometry to one O(4), two equivalent O(1), two equivalent O(3), and four equivalent O(2) atoms. The Y(1)-O(4) bond length is 2.34 Å. Both Y(1)-O(1) bond lengths are 2.41 Å. Both Y(1)-O(3) bond lengths are 2.47 Å. There are two shorter (2.38 Å) and two longer (2.42 Å) Y(1)-O(2) bond lengths. There are two inequivalent C sites. In the first C site, C(1) is bonded in a distorted bent 120 degrees geometry to two equivalent O(1) atoms. Both C(1)-O(1) bond lengths are 1.26 Å. In the second C site, C(2) is bonded in a trigonal planar geometry to one O(3) and two equivalent O(2) atoms. The C(2)-O(3) bond length is 1.30 Å. Both C(2)-O(2) bond lengths are 1.29 Å. H(1) is bonded in a single-bond geometry to one O(4) atom. The H(1)-O(4) bond length is 0.99 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Y(1) and one C(1) atom. In the second O site, O(4) is bonded in a distorted trigonal planar geometry to one Y(1) and two equivalent H(1) atoms. In the third O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Y(1) and one C(2) atom. In the fourth O site, O(3) is bonded in a distorted T-shaped geometry to two equivalent Y(1) and one C(2) atom. Linkers: 2 [O]C(=O)C([O])=O. Metal clusters: 4 [Y]. The MOF has largest included sphere 3.46 A, density 2.50 g/cm3, surface area 1968.41 m2/g, accessible volume 0.08 cm3/g