KC4H4SO4CH crystallizes in the monoclinic P2_1/c space group. The structure consists of four 02329_fluka molecules inside a KC4H4SO4 framework. In the KC4H4SO4 framework, K(1) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(4), and two equivalent O(1) atoms. The K(1)-O(2) bond length is 2.73 Å. The K(1)-O(3) bond length is 2.84 Å. The K(1)-O(4) bond length is 2.72 Å. There is one shorter (2.67 Å) and one longer (2.88 Å) K(1)-O(1) bond length. There are four inequivalent C sites. In the first C site, C(3) is bonded in a trigonal planar geometry to one C(2), one C(4), and one S(1) atom. The C(3)-C(2) bond length is 1.43 Å. The C(3)-C(4) bond length is 1.38 Å. The C(3)-S(1) bond length is 1.79 Å. In the second C site, C(4) is bonded in a distorted single-bond geometry to one C(3) and one H(4) atom. The C(4)-H(4) bond length is 1.09 Å. In the third C site, C(1) is bonded in a distorted single-bond geometry to one C(2) and one H(3) atom. The C(1)-C(2) bond length is 1.42 Å. The C(1)-H(3) bond length is 1.09 Å. In the fourth C site, C(2) is bonded in a trigonal planar geometry to one C(1), one C(2), and one C(3) atom. The C(2)-C(2) bond length is 1.44 Å. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(4) atom. The H(1)-O(4) 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 0.98 Å. In the third H site, H(3) is bonded in a single-bond geometry to one C(1) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one C(4) atom. S(1) is bonded in a distorted trigonal non-coplanar geometry to one C(3), one O(1), one O(2), and one O(3) atom. The S(1)-O(1) bond length is 1.47 Å. The S(1)-O(2) bond length is 1.48 Å. The S(1)-O(3) bond length is 1.48 Å. There are four inequivalent O sites. In the first O site, O(4) is bonded in a water-like geometry to one K(1), one H(1), and one H(2) atom. In the second O site, O(1) is bonded in a distorted single-bond geometry to two equivalent K(1) and one S(1) atom. In the third O site, O(2) is bonded in a distorted single-bond geometry to one K(1) and one S(1) atom. In the fourth O site, O(3) is bonded in a distorted single-bond geometry to one K(1) and one S(1) atom. Linkers: 2 [O]S([O])([O])c1cccc2c(S([O])([O])[O])cccc12. Metal clusters: 4 [K]. RCSR code: sit. The MOF has largest included sphere 1.82 A, density 1.83 g/cm3, surface area 2374.34 m2/g, accessible volume 0.05 cm3/g