KGdC2H2SO9 crystallizes in the monoclinic P2_1/c space group. K(1) is bonded in a 9-coordinate geometry to one O(2), one O(3), one O(5), one O(6), one O(7), two equivalent O(8), and two equivalent O(9) atoms. The K(1)-O(2) bond length is 2.90 Å. The K(1)-O(3) bond length is 2.74 Å. The K(1)-O(5) bond length is 2.96 Å. The K(1)-O(6) bond length is 2.97 Å. The K(1)-O(7) bond length is 2.77 Å. There is one shorter (2.90 Å) and one longer (3.05 Å) K(1)-O(8) bond length. There is one shorter (3.02 Å) and one longer (3.17 Å) K(1)-O(9) bond length. Gd(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(6), one O(7), one O(8), and one O(9) atom. The Gd(1)-O(1) bond length is 2.34 Å. The Gd(1)-O(2) bond length is 2.37 Å. The Gd(1)-O(4) bond length is 2.35 Å. The Gd(1)-O(5) bond length is 2.32 Å. The Gd(1)-O(6) bond length is 2.44 Å. The Gd(1)-O(7) bond length is 2.44 Å. The Gd(1)-O(8) bond length is 2.45 Å. The Gd(1)-O(9) bond length is 2.42 Å. There are two inequivalent C sites. In the first C site, C(1) is bonded in a distorted bent 120 degrees geometry to one O(6) and one O(8) atom. The C(1)-O(6) bond length is 1.28 Å. The C(1)-O(8) bond length is 1.26 Å. In the second C site, C(2) is bonded in a distorted bent 120 degrees geometry to one O(7) and one O(9) atom. The C(2)-O(7) bond length is 1.27 Å. The C(2)-O(9) bond length is 1.26 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(2) atom. The H(1)-O(2) bond length is 0.99 Å. In the second H site, H(2) is bonded in a distorted single-bond geometry to one O(2) atom. The H(2)-O(2) bond length is 1.00 Å. S(1) is bonded in a tetrahedral geometry to one O(1), one O(3), one O(4), and one O(5) atom. The S(1)-O(1) bond length is 1.49 Å. The S(1)-O(3) bond length is 1.47 Å. The S(1)-O(4) bond length is 1.49 Å. The S(1)-O(5) bond length is 1.50 Å. There are nine inequivalent O sites. In the first O site, O(2) is bonded in a distorted water-like geometry to one K(1), one Gd(1), one H(1), and one H(2) atom. In the second O site, O(3) is bonded in a distorted bent 120 degrees geometry to one K(1) and one S(1) atom. In the third O site, O(4) is bonded in a bent 150 degrees geometry to one Gd(1) and one S(1) atom. In the fourth O site, O(5) is bonded in a 3-coordinate geometry to one K(1), one Gd(1), and one S(1) atom. In the fifth O site, O(9) is bonded in a distorted single-bond geometry to two equivalent K(1), one Gd(1), and one C(2) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one K(1), one Gd(1), and one C(1) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one K(1), one Gd(1), and one C(2) atom. In the eighth O site, O(8) is bonded in a distorted single-bond geometry to two equivalent K(1), one Gd(1), and one C(1) atom. In the ninth O site, O(1) is bonded in a bent 150 degrees geometry to one Gd(1) and one S(1) atom. Linkers: 4 [O]C(=O)C([O])=O. Metal clusters: 4 [K] ,4 [Gd]. The MOF has largest included sphere 1.23 A, density 3.48 g/cm3, surface area 663.48 m2/g, accessible volume 0.01 cm3/g