LaC4H4O5 crystallizes in the monoclinic P2_1/c space group. La(1) is bonded in a 6-coordinate geometry to one O(2), one O(3), one O(4), one O(5), and two equivalent O(1) atoms. The La(1)-O(2) bond length is 2.47 Å. The La(1)-O(3) bond length is 2.56 Å. The La(1)-O(4) bond length is 2.55 Å. The La(1)-O(5) bond length is 2.62 Å. There is one shorter (2.60 Å) and one longer (2.63 Å) La(1)-O(1) bond length. There are four inequivalent C sites. In the first C site, C(1) is bonded in a distorted trigonal planar geometry to one C(2), one O(1), and one O(2) atom. The C(1)-C(2) bond length is 1.50 Å. The C(1)-O(1) bond length is 1.26 Å. The C(1)-O(2) bond length is 1.24 Å. In the second C site, C(2) is bonded in a distorted trigonal non-coplanar geometry to one C(1); two equivalent H(1,2); and one O(3) atom. Both C(2)-H(1,2) bond lengths are 0.97 Å. The C(2)-O(3) bond length is 1.41 Å. In the third C site, C(3) is bonded in a distorted trigonal non-coplanar geometry to one C(4); two equivalent H(3,4); and one O(3) atom. The C(3)-C(4) bond length is 1.50 Å. Both C(3)-H(3,4) bond lengths are 0.97 Å. The C(3)-O(3) bond length is 1.43 Å. In the fourth C site, C(4) is bonded in a distorted trigonal planar geometry to one C(3), one O(4), and one O(5) atom. The C(4)-O(4) bond length is 1.27 Å. The C(4)-O(5) bond length is 1.26 Å. There are two inequivalent H sites. In the first H site, H(1,2) is bonded in a single-bond geometry to one C(2) atom. In the second H site, H(3,4) is bonded in a single-bond geometry to one C(3) atom. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent La(1) and one C(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one La(1) and one C(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one La(1), one C(2), and one C(3) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one La(1) and one C(4) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one La(1) and one C(4) atom. Linkers: 4 [O]C(=O)COCC([O])=O. Metal clusters: 4 [La]. The MOF has largest included sphere 5.24 A, density 1.73 g/cm3, surface area 2580.90 m2/g, accessible volume 0.27 cm3/g