CaH2(CO2)2 crystallizes in the tetragonal P4_32_12 space group. Ca(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form distorted corner-sharing CaO6 octahedra. The corner-sharing octahedral tilt angles are 62°. Both Ca(1)-O(2) bond lengths are 2.30 Å. There are two shorter (2.38 Å) and two longer (2.48 Å) Ca(1)-O(1) bond lengths. C(1) is bonded in a trigonal planar geometry to one H(1), one O(1), and one O(2) atom. The C(1)-H(1) bond length is 1.11 Å. The C(1)-O(1) bond length is 1.28 Å. The C(1)-O(2) bond length is 1.26 Å. H(1) is bonded in a single-bond geometry to one C(1) atom. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Ca(1) and one C(1) atom. In the second O site, O(2) is bonded in a distorted linear geometry to one Ca(1) and one C(1) atom. Linkers: 8 [O]C=O. Metal clusters: 4 [Ca]. RCSR code: dia. The MOF has largest included sphere 1.50 A, density 2.00 g/cm3, surface area 3224.76 m2/g, accessible volume 0.04 cm3/g