EuH4(C2O)6 crystallizes in the monoclinic P2_1/c space group. Eu(1) is bonded in a 7-coordinate geometry to one O(2), one O(3), one O(4), one O(5), one O(6), and two equivalent O(1) atoms. The Eu(1)-O(2) bond length is 2.63 Å. The Eu(1)-O(3) bond length is 2.47 Å. The Eu(1)-O(4) bond length is 2.36 Å. The Eu(1)-O(5) bond length is 2.31 Å. The Eu(1)-O(6) bond length is 2.53 Å. There is one shorter (2.49 Å) and one longer (2.55 Å) Eu(1)-O(1) bond length. There are twelve inequivalent C sites. In the first C site, C(1) is bonded in a distorted single-bond geometry to one C(4) and one H(3) atom. The C(1)-C(4) bond length is 1.39 Å. The C(1)-H(3) bond length is 0.93 Å. In the second C site, C(2) is bonded in a distorted bent 120 degrees geometry to one C(9), one O(1), and one O(2) atom. The C(2)-C(9) bond length is 1.51 Å. The C(2)-O(1) bond length is 1.28 Å. The C(2)-O(2) bond length is 1.24 Å. In the third C site, C(3) is bonded in a distorted single-bond geometry to one C(12), one C(4), and one H(4) atom. The C(3)-C(12) bond length is 1.37 Å. The C(3)-C(4) bond length is 1.39 Å. The C(3)-H(4) bond length is 0.93 Å. In the fourth C site, C(4) is bonded in a trigonal planar geometry to one C(1), one C(11), and one C(3) atom. The C(4)-C(11) bond length is 1.51 Å. In the fifth C site, C(5) is bonded in a trigonal planar geometry to one C(10), one C(12), and one C(9) atom. The C(5)-C(10) bond length is 1.39 Å. The C(5)-C(12) bond length is 1.52 Å. The C(5)-C(9) bond length is 1.39 Å. In the sixth C site, C(6) is bonded in a distorted bent 120 degrees geometry to one C(7), one O(4), and one O(5) atom. The C(6)-C(7) bond length is 1.52 Å. The C(6)-O(4) bond length is 1.26 Å. The C(6)-O(5) bond length is 1.25 Å. In the seventh C site, C(7) is bonded in a trigonal planar geometry to one C(12), one C(6), and one C(8) atom. The C(7)-C(12) bond length is 1.40 Å. The C(7)-C(8) bond length is 1.40 Å. In the eighth C site, C(8) is bonded in a distorted single-bond geometry to one C(7) and one H(2) atom. The C(8)-H(2) bond length is 0.93 Å. In the ninth C site, C(9) is bonded in a trigonal planar geometry to one C(10), one C(2), and one C(5) atom. The C(9)-C(10) bond length is 1.39 Å. In the tenth C site, C(10) is bonded in a distorted single-bond geometry to one C(5), one C(9), and one H(1) atom. The C(10)-H(1) bond length is 0.93 Å. In the eleventh C site, C(11) is bonded in a distorted bent 120 degrees geometry to one C(4), one O(3), and one O(6) atom. The C(11)-O(3) bond length is 1.27 Å. The C(11)-O(6) bond length is 1.25 Å. In the twelfth C site, C(12) is bonded in a trigonal planar geometry to one C(3), one C(5), and one C(7) atom. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one C(10) atom. In the second H site, H(2) is bonded in a single-bond geometry to one C(8) atom. In the third H site, H(3) is bonded in a single-bond geometry to one C(1) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one C(3) atom. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to two equivalent Eu(1) and one C(2) atom. In the second O site, O(2) is bonded in a single-bond geometry to one Eu(1) and one C(2) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Eu(1) and one C(11) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Eu(1) and one C(6) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Eu(1) and one C(6) atom. In the sixth O site, O(6) is bonded in a distorted L-shaped geometry to one Eu(1) and one C(11) atom. Linkers: 4 [O]C(=O)c1ccc([C]=O)c(-c2cc(C([O])=O)c(-c3cc(C([O])=O)ccc3C([O])=O)cc2C([O])=O)c1 ,3 [O]C(=O)c1ccc(C([O])=O)c(-c2cc(C([O])=O)c(-c3cc(C([O])=O)ccc3C([O])=O)cc2C([O])=O)c1. Metal clusters: 4 [Eu]. The MOF has largest included sphere 4.02 A, density 1.80 g/cm3, surface area 2838.80 m2/g, accessible volume 0.26 cm3/g