TlCHO2 is alpha As structured and crystallizes in the orthorhombic Pna2_1 space group. The structure is zero-dimensional and consists of four thallous formate molecules. Tl(1) is bonded in a single-bond geometry to one O(2) atom. The Tl(1)-O(2) bond length is 2.72 Å. 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 1.26 Å. The C(1)-O(2) bond length is 1.27 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 single-bond geometry to one C(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Tl(1) and one C(1) atom. Linkers: 4 [O]C=O. Metal clusters: 4 [Tl]. The MOF has largest included sphere 1.40 A, density 5.23 g/cm3, surface area 1309.70 m2/g, accessible volume 0.04 cm3/g