Er2CuC12H2(NO3)4 crystallizes in the monoclinic C2/c space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a pentagonal planar geometry to one N(2), one N(4), one O(3), one O(4), and one O(7) atom. The Er(1)-N(2) bond length is 2.49 Å. The Er(1)-N(4) bond length is 2.46 Å. The Er(1)-O(3) bond length is 2.31 Å. The Er(1)-O(4) bond length is 2.34 Å. The Er(1)-O(7) bond length is 2.29 Å. In the second Er site, Er(2) is bonded in a pentagonal planar geometry to one O(10), one O(11), one O(12), one O(8), and one O(9) atom. The Er(2)-O(10) bond length is 2.32 Å. The Er(2)-O(11) bond length is 2.34 Å. The Er(2)-O(12) bond length is 2.37 Å. The Er(2)-O(8) bond length is 2.22 Å. The Er(2)-O(9) bond length is 2.44 Å. Cu(1) is bonded in a square co-planar geometry to one N(1), one N(3), one O(1), and one O(5) atom. The Cu(1)-N(1) bond length is 1.89 Å. The Cu(1)-N(3) bond length is 1.91 Å. The Cu(1)-O(1) bond length is 1.96 Å. The Cu(1)-O(5) bond length is 1.95 Å. There are thirteen inequivalent C sites. In the first C site, C(1) is bonded in a distorted bent 120 degrees geometry to one C(2), one O(1), and one O(2) atom. The C(1)-C(2) bond length is 1.47 Å. The C(1)-O(1) bond length is 1.29 Å. The C(1)-O(2) bond length is 1.22 Å. In the second C site, C(2) is bonded in a distorted single-bond geometry to one C(1), one C(3), and one N(1) atom. The C(2)-C(3) bond length is 1.39 Å. The C(2)-N(1) bond length is 1.34 Å. In the third C site, C(3) is bonded in a distorted single-bond geometry to one C(2) and one H(1) atom. The C(3)-H(1) bond length is 0.93 Å. In the fourth C site, C(4) is bonded in a distorted single-bond geometry to one N(2) atom. The C(4)-N(2) bond length is 1.33 Å. In the fifth C site, C(5) is bonded in a distorted bent 120 degrees geometry to one O(3) and one O(4) atom. The C(5)-O(3) bond length is 1.26 Å. The C(5)-O(4) bond length is 1.24 Å. In the sixth C site, C(6) is bonded in a distorted bent 120 degrees geometry to one C(7), one O(5), and one O(6) atom. The C(6)-C(7) bond length is 1.46 Å. The C(6)-O(5) bond length is 1.30 Å. The C(6)-O(6) bond length is 1.23 Å. In the seventh C site, C(7) is bonded in a distorted single-bond geometry to one C(6), one C(8), and one N(3) atom. The C(7)-C(8) bond length is 1.39 Å. The C(7)-N(3) bond length is 1.34 Å. In the eighth C site, C(8) is bonded in a distorted single-bond geometry to one C(7), one C(9), and one H(2) atom. The C(8)-C(9) bond length is 1.38 Å. The C(8)-H(2) bond length is 0.93 Å. In the ninth C site, C(9) is bonded in a distorted single-bond geometry to one C(10), one C(8), and one N(4) atom. The C(9)-C(10) bond length is 1.47 Å. The C(9)-N(4) bond length is 1.35 Å. In the tenth C site, C(10) is bonded in a distorted bent 120 degrees geometry to one C(9), one O(7), and one O(8) atom. The C(10)-O(7) bond length is 1.26 Å. The C(10)-O(8) bond length is 1.26 Å. In the eleventh C site, C(11) is bonded in a distorted bent 120 degrees geometry to one O(11) and one O(12) atom. The C(11)-O(11) bond length is 1.24 Å. The C(11)-O(12) bond length is 1.26 Å. In the twelfth C site, C(12) is bonded in a distorted bent 120 degrees geometry to two equivalent O(9) atoms. Both C(12)-O(9) bond lengths are 1.26 Å. In the thirteenth C site, C(13) is bonded in a distorted bent 120 degrees geometry to two equivalent O(10) atoms. Both C(13)-O(10) bond lengths are 1.24 Å. There are four inequivalent N sites. In the first N site, N(1) is bonded in a 3-coordinate geometry to one Cu(1), one C(2), and one N(2) atom. The N(1)-N(2) bond length is 1.34 Å. In the second N site, N(2) is bonded in a 3-coordinate geometry to one Er(1), one C(4), and one N(1) atom. In the third N site, N(3) is bonded in a 3-coordinate geometry to one Cu(1), one C(7), and one N(4) atom. The N(3)-N(4) bond length is 1.33 Å. In the fourth N site, N(4) is bonded in a 3-coordinate geometry to one Er(1), one C(9), and one N(3) atom. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one C(3) atom. In the second H site, H(2) is bonded in a single-bond geometry to one C(8) atom. There are twelve inequivalent O sites. In the first O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Er(1) and one C(5) atom. In the second O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Er(1) and one C(5) atom. In the third O site, O(5) is bonded in a bent 120 degrees geometry to one Cu(1) and one C(6) atom. In the fourth O site, O(6) is bonded in a single-bond geometry to one C(6) atom. In the fifth O site, O(7) is bonded in a bent 120 degrees geometry to one Er(1) and one C(10) atom. In the sixth O site, O(8) is bonded in a bent 150 degrees geometry to one Er(2) and one C(10) atom. In the seventh O site, O(9) is bonded in a distorted single-bond geometry to one Er(2) and one C(12) atom. In the eighth O site, O(10) is bonded in a distorted bent 120 degrees geometry to one Er(2) and one C(13) atom. In the ninth O site, O(11) is bonded in a bent 120 degrees geometry to one Er(2) and one C(11) atom. In the tenth O site, O(12) is bonded in a bent 120 degrees geometry to one Er(2) and one C(11) atom. In the eleventh O site, O(1) is bonded in a bent 120 degrees geometry to one Cu(1) and one C(1) atom. In the twelfth O site, O(2) is bonded in a single-bond geometry to one C(1) atom. Linkers: 3 [O]C(=O)C1=NN=C(C([O])=O)[CH]1 ,3 [O]C(=O)[C]1C=C(C([O])=O)N=N1 ,3 [O]C(=O)C([O])=O ,2 [O]C(=O)C1=CC(C([O])=O)=N[N]1. Metal clusters: 8 [Er] ,4 [Cu]. The MOF has largest included sphere 4.14 A, density 2.16 g/cm3, surface area 2627.71 m2/g, accessible volume 0.20 cm3/g