Cs2C7NH3O5 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 7-coordinate geometry to one H(1), one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms. The Cs(1)-H(1) bond length is 3.17 Å. The Cs(1)-O(1) bond length is 3.29 Å. The Cs(1)-O(4) bond length is 3.05 Å. There is one shorter (3.09 Å) and one longer (3.28 Å) Cs(1)-O(2) bond length. There is one shorter (2.92 Å) and one longer (2.98 Å) Cs(1)-O(3) bond length. In the second Cs site, Cs(2) is bonded in a 9-coordinate geometry to one H(3), one O(2), two equivalent O(1), two equivalent O(4), and three equivalent O(5) atoms. The Cs(2)-H(3) bond length is 3.20 Å. The Cs(2)-O(2) bond length is 3.12 Å. There is one shorter (3.23 Å) and one longer (3.48 Å) Cs(2)-O(1) bond length. There is one shorter (3.27 Å) and one longer (3.50 Å) Cs(2)-O(4) bond length. There is one shorter (2.97 Å) and two longer (3.27 Å) Cs(2)-O(5) bond lengths. There are seven inequivalent C sites. In the first C site, C(4) is bonded in a distorted single-bond geometry to one C(3) and one O(3) atom. The C(4)-C(3) bond length is 1.45 Å. The C(4)-O(3) bond length is 1.27 Å. In the second C site, C(5) is bonded in a distorted single-bond geometry to one C(6) and one H(3) atom. The C(5)-C(6) bond length is 1.37 Å. The C(5)-H(3) bond length is 1.09 Å. In the third C site, C(6) is bonded in a distorted trigonal planar geometry to one C(5), one C(7), and one N(1) atom. The C(6)-C(7) bond length is 1.52 Å. The C(6)-N(1) bond length is 1.35 Å. In the fourth C site, C(7) is bonded in a distorted bent 120 degrees geometry to one C(6), one O(4), and one O(5) atom. The C(7)-O(4) bond length is 1.27 Å. The C(7)-O(5) bond length is 1.26 Å. In the fifth C site, C(1) is bonded in a distorted trigonal planar geometry to one C(2), one C(3), and one N(1) atom. The C(1)-C(2) bond length is 1.52 Å. The C(1)-C(3) bond length is 1.37 Å. The C(1)-N(1) bond length is 1.36 Å. In the sixth C site, C(2) is bonded in a distorted bent 120 degrees geometry to one C(1), one O(1), and one O(2) atom. The C(2)-O(1) bond length is 1.27 Å. The C(2)-O(2) bond length is 1.27 Å. In the seventh C site, C(3) is bonded in a distorted trigonal planar geometry to one C(1), one C(4), and one H(2) atom. The C(3)-H(2) bond length is 1.09 Å. N(1) is bonded in a trigonal planar geometry to one C(1), one C(6), and one H(1) atom. The N(1)-H(1) bond length is 1.02 Å. There are three inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one Cs(1) and one N(1) atom. In the second H site, H(2) is bonded in a single-bond geometry to one C(3) atom. In the third H site, H(3) is bonded in a single-bond geometry to one Cs(2) and one C(5) atom. There are five inequivalent O sites. In the first O site, O(4) is bonded in a distorted single-bond geometry to one Cs(1), two equivalent Cs(2), and one C(7) atom. In the second O site, O(5) is bonded in a distorted single-bond geometry to three equivalent Cs(2) and one C(7) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to two equivalent Cs(1) and one C(4) atom. In the fourth O site, O(1) is bonded in a single-bond geometry to one Cs(1), two equivalent Cs(2), and one C(2) atom. In the fifth O site, O(2) is bonded in a distorted single-bond geometry to one Cs(2), two equivalent Cs(1), and one C(2) atom. Linkers: 4 [O]C(=O)c1cc(=O)cc(C([O])=O)[nH]1. Metal clusters: 8 [Cs]. The MOF has largest included sphere 2.00 A, density 2.82 g/cm3, surface area 2637.96 m2/g, accessible volume 0.07 cm3/g