CsH5(C2O3)2 crystallizes in the monoclinic P2_1/c space group. Cs(1) is bonded in a 9-coordinate geometry to one H(5), one O(3), one O(6), two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms. The Cs(1)-H(5) bond length is 3.14 Å. The Cs(1)-O(3) bond length is 3.02 Å. The Cs(1)-O(6) bond length is 3.28 Å. There is one shorter (3.11 Å) and one longer (3.12 Å) Cs(1)-O(2) bond length. There is one shorter (3.23 Å) and one longer (3.24 Å) Cs(1)-O(4) bond length. There is one shorter (3.04 Å) and one longer (3.05 Å) Cs(1)-O(5) bond length. There are four inequivalent C sites. In the first C site, C(3) is bonded in a distorted water-like geometry to one H(5) and one O(4) atom. The C(3)-H(5) bond length is 1.10 Å. The C(3)-O(4) bond length is 1.42 Å. In the second C site, C(4) is bonded in a distorted bent 120 degrees geometry to one O(5) and one O(6) atom. The C(4)-O(5) bond length is 1.23 Å. The C(4)-O(6) bond length is 1.33 Å. In the third 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 1.28 Å. The C(1)-O(2) bond length is 1.26 Å. In the fourth C site, C(2) is bonded in a distorted water-like geometry to one H(4) and one O(3) atom. The C(2)-H(4) bond length is 1.10 Å. The C(2)-O(3) bond length is 1.41 Å. There are five inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(3) atom. The H(1)-O(3) bond length is 0.99 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(4) atom. The H(2)-O(4) bond length is 1.00 Å. In the third H site, H(3) is bonded in a linear geometry to one O(1) and one O(6) atom. The H(3)-O(1) bond length is 1.50 Å. The H(3)-O(6) bond length is 1.05 Å. In the fourth H site, H(4) is bonded in a single-bond geometry to one C(2) atom. In the fifth H site, H(5) is bonded in a single-bond geometry to one Cs(1) and one C(3) atom. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one C(1) and one H(3) atom. In the second O site, O(2) is bonded in a single-bond geometry to two equivalent Cs(1) and one C(1) atom. In the third O site, O(6) is bonded in a distorted water-like geometry to one Cs(1), one C(4), and one H(3) atom. In the fourth O site, O(3) is bonded in a distorted water-like geometry to one Cs(1), one C(2), and one H(1) atom. In the fifth O site, O(4) is bonded in a water-like geometry to two equivalent Cs(1), one C(3), and one H(2) atom. In the sixth O site, O(5) is bonded in a single-bond geometry to two equivalent Cs(1) and one C(4) atom. Linkers: 2 [O]C(=O)[C@@H](O)[C@H](O)C(=O)O ,2 [O]C(=O)[C@H](O)[C@@H](O)C(=O)O. Metal clusters: 4 [Cs]. The MOF has largest included sphere 2.07 A, density 2.57 g/cm3, surface area 2640.86 m2/g, accessible volume 0.07 cm3/g