CaC6H2SO4 crystallizes in the orthorhombic Pbcm space group. Ca(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form edge-sharing CaO6 octahedra. Both Ca(1)-O(1) bond lengths are 2.31 Å. There are two shorter (2.39 Å) and two longer (2.40 Å) Ca(1)-O(2) bond lengths. There are three inequivalent C sites. In the first C site, C(1) is bonded in a trigonal planar geometry to one C(2), one C(3), and one S(1) atom. The C(1)-C(2) bond length is 1.48 Å. The C(1)-C(3) bond length is 1.39 Å. The C(1)-S(1) bond length is 1.72 Å. In the second 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 1.26 Å. The C(2)-O(2) bond length is 1.29 Å. In the third C site, C(3) is bonded in a distorted single-bond geometry to one C(1), one C(3), and one H(1) atom. The C(3)-C(3) bond length is 1.41 Å. The C(3)-H(1) bond length is 1.09 Å. H(1) is bonded in a single-bond geometry to one C(3) atom. S(1) is bonded in an L-shaped geometry to two equivalent C(1) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Ca(1) and one C(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Ca(1) and one C(2) atom. Linkers: 4 [O]C(=O)c1ccc(C([O])=O)s1. Metal clusters: 4 [Ca]. RCSR code: sql. The MOF has largest included sphere 1.36 A, density 2.08 g/cm3, surface area 2690.78 m2/g, accessible volume 0.03 cm3/g