KC3H5O4 crystallizes in the monoclinic P2_1/c space group. K(1) is bonded in a 9-coordinate geometry to two equivalent H(2), one O(3), one O(4), two equivalent O(2), and three equivalent O(1) atoms. There is one shorter (2.92 Å) and one longer (3.03 Å) K(1)-H(2) bond length. The K(1)-O(3) bond length is 3.01 Å. The K(1)-O(4) bond length is 2.73 Å. There is one shorter (2.75 Å) and one longer (2.95 Å) K(1)-O(2) bond length. There are two shorter (2.69 Å) and one longer (2.98 Å) K(1)-O(1) bond length. There are three inequivalent C sites. In the first C site, C(3) is bonded in a distorted trigonal non-coplanar geometry to one H(4), one H(5), and one O(3) atom. The C(3)-H(4) bond length is 1.10 Å. The C(3)-H(5) bond length is 1.10 Å. The C(3)-O(3) bond length is 1.43 Å. In the second C site, C(1) is bonded in a distorted bent 120 degrees geometry to one O(1) and one O(4) atom. The C(1)-O(1) bond length is 1.26 Å. The C(1)-O(4) bond length is 1.28 Å. In the third C site, C(2) is bonded in a distorted water-like geometry to one H(3) and one O(2) atom. The C(2)-H(3) bond length is 1.11 Å. The C(2)-O(2) bond length is 1.43 Å. There are five 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 1.00 Å. In the second H site, H(2) is bonded in a distorted linear geometry to two equivalent K(1), one O(3), and one O(4) atom. The H(2)-O(3) bond length is 1.03 Å. The H(2)-O(4) bond length is 1.56 Å. In the third H site, H(3) is bonded in a single-bond geometry to one C(2) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one C(3) atom. In the fifth H site, H(5) is bonded in a single-bond geometry to one C(3) atom. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to three equivalent K(1) and one C(1) atom. In the second O site, O(2) is bonded in a distorted water-like geometry to two equivalent K(1), one C(2), and one H(1) atom. In the third O site, O(3) is bonded in a distorted water-like geometry to one K(1), one C(3), and one H(2) atom. In the fourth O site, O(4) is bonded in a distorted water-like geometry to one K(1), one C(1), and one H(2) atom. Linkers: 2 [O]C(=O)[C@H](O)CO ,2 [O]C(=O)[C@@H](O)CO. Metal clusters: 4 [K]. The MOF has largest included sphere 1.16 A, density 1.83 g/cm3, surface area 1794.99 m2/g, accessible volume 0.01 cm3/g