CsC6NH4O3 crystallizes in the monoclinic P2_1/c space group. Cs(1) is bonded in a 7-coordinate geometry to one H(3), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. The Cs(1)-H(3) bond length is 3.15 Å. There is one shorter (2.94 Å) and one longer (3.06 Å) Cs(1)-O(1) bond length. There is one shorter (2.98 Å) and one longer (3.06 Å) Cs(1)-O(2) bond length. There is one shorter (3.19 Å) and one longer (3.29 Å) Cs(1)-O(3) bond length. There are six inequivalent C sites. In the first C site, C(4) is bonded in a distorted single-bond geometry to one C(3) and one H(4) atom. The C(4)-C(3) bond length is 1.38 Å. The C(4)-H(4) bond length is 1.09 Å. In the second C site, C(5) is bonded in a distorted bent 120 degrees geometry to one N(1) and one O(3) atom. The C(5)-N(1) bond length is 1.39 Å. The C(5)-O(3) bond length is 1.27 Å. In the third C site, C(6) is bonded in a distorted bent 120 degrees geometry to one C(1), one O(1), and one O(2) atom. The C(6)-C(1) bond length is 1.52 Å. The C(6)-O(1) bond length is 1.27 Å. The C(6)-O(2) bond length is 1.27 Å. In the fourth C site, C(1) is bonded in a distorted trigonal planar geometry to one C(2), one C(6), and one N(1) atom. The C(1)-C(2) bond length is 1.38 Å. The C(1)-N(1) bond length is 1.36 Å. In the fifth C site, C(2) is bonded in a distorted trigonal planar geometry to one C(1), one C(3), and one H(2) atom. The C(2)-C(3) bond length is 1.41 Å. The C(2)-H(2) bond length is 1.09 Å. In the sixth C site, C(3) is bonded in a distorted trigonal planar geometry to one C(2), one C(4), and one H(3) atom. The C(3)-H(3) bond length is 1.09 Å. N(1) is bonded in a trigonal planar geometry to one C(1), one C(5), and one H(1) atom. The N(1)-H(1) bond length is 1.04 Å. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one N(1) atom. In the second H site, H(2) is bonded in a single-bond geometry to one C(2) atom. In the third H site, H(3) is bonded in a single-bond geometry to one Cs(1) and one C(3) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one C(4) atom. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to two equivalent Cs(1) and one C(6) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to two equivalent Cs(1) and one C(6) atom. In the third O site, O(3) is bonded in a single-bond geometry to two equivalent Cs(1) and one C(5) atom. Linkers: 4 [O]C(=O)c1cccc(=O)[nH]1. Metal clusters: 4 [Cs]. The MOF has largest included sphere 2.14 A, density 2.34 g/cm3, surface area 3202.63 m2/g, accessible volume 0.12 cm3/g