GdH9(CO2)4 crystallizes in the monoclinic P2_1/c space group. Gd(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(6), one O(8), and two equivalent O(7) atoms. The Gd(1)-O(1) bond length is 2.43 Å. The Gd(1)-O(2) bond length is 2.44 Å. The Gd(1)-O(3) bond length is 2.51 Å. The Gd(1)-O(4) bond length is 2.37 Å. The Gd(1)-O(6) bond length is 2.50 Å. The Gd(1)-O(8) bond length is 2.41 Å. There is one shorter (2.25 Å) and one longer (2.28 Å) Gd(1)-O(7) bond length. There are four inequivalent C sites. In the first C site, C(1) is bonded in a distorted bent 120 degrees geometry to one O(4) and one O(8) atom. The C(1)-O(4) bond length is 1.25 Å. The C(1)-O(8) bond length is 1.28 Å. In the second C site, C(2) is bonded in a distorted bent 120 degrees geometry to one O(2) and one O(5) atom. The C(2)-O(2) bond length is 1.27 Å. The C(2)-O(5) bond length is 1.27 Å. In the third C site, C(3) is bonded in a distorted trigonal non-coplanar geometry to one H(5), one H(6), and one O(3) atom. The C(3)-H(5) bond length is 1.10 Å. The C(3)-H(6) bond length is 1.11 Å. The C(3)-O(3) bond length is 1.42 Å. In the fourth C site, C(4) is bonded in a distorted trigonal non-coplanar geometry to two equivalent H(7,8) and one O(3) atom. Both C(4)-H(7,8) bond lengths are 1.10 Å. The C(4)-O(3) bond length is 1.43 Å. There are eight inequivalent H sites. In the first H site, H(1) is bonded in a distorted linear geometry to one O(1) and one O(5) atom. The H(1)-O(1) bond length is 1.00 Å. The H(1)-O(5) bond length is 1.63 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(1) and one O(5) atom. The H(2)-O(1) bond length is 1.00 Å. The H(2)-O(5) bond length is 1.70 Å. In the third H site, H(3) is bonded in a single-bond geometry to one O(6) atom. The H(3)-O(6) bond length is 0.99 Å. In the fourth H site, H(4) is bonded in a single-bond geometry to one O(6) atom. The H(4)-O(6) bond length is 0.98 Å. In the fifth H site, H(5) is bonded in a single-bond geometry to one C(3) atom. In the sixth H site, H(6) is bonded in a single-bond geometry to one C(3) atom. In the seventh H site, H(7,8) is bonded in a single-bond geometry to one C(4) atom. In the eighth H site, H(9) is bonded in a single-bond geometry to one O(7) atom. The H(9)-O(7) bond length is 0.97 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a water-like geometry to one Gd(1), one H(1), and one H(2) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Gd(1) and one C(2) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Gd(1), one C(3), and one C(4) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Gd(1) and one C(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one C(2), one H(1), and one H(2) atom. In the sixth O site, O(6) is bonded in a water-like geometry to one Gd(1), one H(3), and one H(4) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to two equivalent Gd(1) and one H(9) atom. In the eighth O site, O(8) is bonded in a distorted single-bond geometry to one Gd(1) and one C(1) atom. Linkers: 2 [O]C(=O)COCC([O])=O ,4 [OH]. Metal clusters: 4 [Gd]. The MOF has largest included sphere 1.64 A, density 2.79 g/cm3, surface area 2458.45 m2/g, accessible volume 0.06 cm3/g