KC4H3S(NO)2 crystallizes in the monoclinic P2/c space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to two equivalent S(1) and four equivalent O(1) atoms. Both K(1)-S(1) bond lengths are 3.22 Å. There are two shorter (2.74 Å) and two longer (2.84 Å) K(1)-O(1) bond lengths. In the second K site, K(2) is bonded in a 6-coordinate geometry to two equivalent S(1) and four equivalent O(2) atoms. Both K(2)-S(1) bond lengths are 3.21 Å. There are two shorter (2.74 Å) and two longer (3.07 Å) K(2)-O(2) bond lengths. There are four inequivalent C sites. In the first C site, C(1) is bonded in a distorted single-bond geometry to one C(4) and one H(2) atom. The C(1)-C(4) bond length is 1.41 Å. The C(1)-H(2) bond length is 1.09 Å. In the second C site, C(2) is bonded in a distorted trigonal planar geometry to one N(1), one N(2), and one S(1) atom. The C(2)-N(1) bond length is 1.36 Å. The C(2)-N(2) bond length is 1.36 Å. The C(2)-S(1) bond length is 1.69 Å. In the third C site, C(3) is bonded in a distorted bent 120 degrees geometry to one N(2) and one O(1) atom. The C(3)-N(2) bond length is 1.40 Å. The C(3)-O(1) bond length is 1.28 Å. In the fourth C site, C(4) is bonded in a distorted bent 120 degrees geometry to one C(1), one N(1), and one O(2) atom. The C(4)-N(1) bond length is 1.40 Å. The C(4)-O(2) bond length is 1.27 Å. There are two inequivalent N sites. In the first N site, N(1) is bonded in a trigonal planar geometry to one C(2), one C(4), and one H(3) atom. The N(1)-H(3) bond length is 1.05 Å. In the second N site, N(2) is bonded in a trigonal planar geometry to one C(2), one C(3), and one H(1) atom. The N(2)-H(1) bond length is 1.05 Å. There are three inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one N(2) atom. In the second H site, H(2) is bonded in a single-bond geometry to one C(1) atom. In the third H site, H(3) is bonded in a single-bond geometry to one N(1) atom. S(1) is bonded in a 3-coordinate geometry to one K(1), one K(2), and one C(2) atom. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to two equivalent K(1) and one C(3) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to two equivalent K(2) and one C(4) atom. Linkers: 4 O=C1[CH]C(=O)NC(=S)N1. Metal clusters: 4 [K]. The MOF has largest included sphere 1.45 A, density 1.95 g/cm3, surface area 1719.31 m2/g, accessible volume 0.04 cm3/g