CsH2(CO2)3(CH2)2CHO crystallizes in the orthorhombic Pna2_1 space group. The structure consists of eight 02329_fluka molecules and four methanol molecules inside a CsH2(CO2)3 framework. In the CsH2(CO2)3 framework, Cs(1) is bonded in a 5-coordinate geometry to one O(2), one O(5), one O(6), and two equivalent O(3) atoms. The Cs(1)-O(2) bond length is 3.34 Å. The Cs(1)-O(5) bond length is 3.23 Å. The Cs(1)-O(6) bond length is 3.07 Å. There is one shorter (3.13 Å) and one longer (3.22 Å) Cs(1)-O(3) bond length. There are three 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 1.32 Å. The C(1)-O(2) bond length is 1.25 Å. In the second C site, C(5) is bonded in a distorted bent 120 degrees geometry to one O(5) and one O(6) atom. The C(5)-O(5) bond length is 1.33 Å. The C(5)-O(6) bond length is 1.24 Å. In the third C site, C(6) is bonded in a distorted bent 120 degrees geometry to one O(3) and one O(4) atom. The C(6)-O(3) bond length is 1.25 Å. The C(6)-O(4) bond length is 1.29 Å. There are two inequivalent H sites. In the first H site, H(6) is bonded in a linear geometry to one O(4) and one O(5) atom. The H(6)-O(4) bond length is 1.38 Å. The H(6)-O(5) bond length is 1.09 Å. In the second H site, H(7) is bonded in a distorted linear geometry to one O(1) and one O(2) atom. The H(7)-O(1) bond length is 1.01 Å. The H(7)-O(2) bond length is 1.60 Å. There are six inequivalent O sites. In the first O site, O(3) is bonded in a single-bond geometry to two equivalent Cs(1) and one C(6) atom. In the second O site, O(4) is bonded in a bent 120 degrees geometry to one C(6) and one H(6) atom. In the third O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Cs(1), one C(5), and one H(6) atom. In the fourth O site, O(6) is bonded in a distorted single-bond geometry to one Cs(1) and one C(5) atom. In the fifth O site, O(2) is bonded in a 2-coordinate geometry to one Cs(1), one C(1), and one H(7) atom. In the sixth O site, O(1) is bonded in a bent 120 degrees geometry to one C(1) and one H(7) atom. Linkers: 4 [O]C(=O)C(O)(CC(=O)O)CC(=O)O. Metal clusters: 4 [Cs]. The MOF has largest included sphere 1.92 A, density 2.31 g/cm3, surface area 3172.50 m2/g, accessible volume 0.07 cm3/g