BaCPH2O5 crystallizes in the monoclinic C2/c space group. Ba(1) is bonded in a 9-coordinate geometry to one O(3), two equivalent O(1), two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms. The Ba(1)-O(3) bond length is 2.96 Å. There is one shorter (2.75 Å) and one longer (2.81 Å) Ba(1)-O(1) bond length. There is one shorter (2.71 Å) and one longer (2.78 Å) Ba(1)-O(2) bond length. There is one shorter (2.82 Å) and one longer (2.93 Å) Ba(1)-O(4) bond length. There is one shorter (2.92 Å) and one longer (2.95 Å) Ba(1)-O(5) bond length. C(1) is bonded in a distorted bent 120 degrees geometry to one O(4) and one O(5) atom. The C(1)-O(4) bond length is 1.26 Å. The C(1)-O(5) bond length is 1.28 Å. P(1) is bonded in a distorted tetrahedral geometry to one H(1), one O(1), one O(2), and one O(3) atom. The P(1)-H(1) bond length is 1.40 Å. The P(1)-O(1) bond length is 1.52 Å. The P(1)-O(2) bond length is 1.52 Å. The P(1)-O(3) bond length is 1.61 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one P(1) atom. In the second H site, H(2) is bonded in a linear geometry to one O(3) and one O(5) atom. The H(2)-O(3) bond length is 1.03 Å. The H(2)-O(5) bond length is 1.57 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one P(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one P(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ba(1), one P(1), and one H(2) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one C(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one C(1), and one H(2) atom. Linkers: 2 [O]C(=O)C([O])=O. Metal clusters: 4 [Ba]. The MOF has largest included sphere 1.21 A, density 3.46 g/cm3, surface area 1719.07 m2/g, accessible volume 0.03 cm3/g