ErC7H(NO3)2 crystallizes in the orthorhombic Pnma space group. Er(1) is bonded in a distorted pentagonal pyramidal geometry to one N(1), one O(2), one O(4), one O(5), and two equivalent O(1) atoms. The Er(1)-N(1) bond length is 2.45 Å. The Er(1)-O(2) bond length is 2.32 Å. The Er(1)-O(4) bond length is 2.21 Å. The Er(1)-O(5) bond length is 2.36 Å. Both Er(1)-O(1) bond lengths are 2.28 Å. There are seven 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(2), and one O(3) atom. The C(1)-C(2) bond length is 1.53 Å. The C(1)-O(2) bond length is 1.28 Å. The C(1)-O(3) 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 1.41 Å. The C(2)-N(1) bond length is 1.33 Å. In the third C site, C(3) is bonded in a distorted trigonal planar geometry to one C(2), one C(4), and one N(2) atom. The C(3)-C(4) bond length is 1.51 Å. The C(3)-N(2) bond length is 1.34 Å. In the fourth C site, C(4) is bonded in a distorted trigonal planar geometry to one C(3) and two equivalent O(1) atoms. Both C(4)-O(1) bond lengths are 1.24 Å. In the fifth C site, C(5) is bonded in a distorted trigonal planar geometry to one C(6), one N(2), and one H(1) atom. The C(5)-C(6) bond length is 1.39 Å. The C(5)-N(2) bond length is 1.34 Å. The C(5)-H(1) bond length is 0.93 Å. In the sixth C site, C(6) is bonded in a distorted single-bond geometry to one C(5), one C(7), and one N(1) atom. The C(6)-C(7) bond length is 1.50 Å. The C(6)-N(1) bond length is 1.32 Å. In the seventh C site, C(7) is bonded in a distorted bent 120 degrees geometry to one C(6), one O(4), and one O(5) atom. The C(7)-O(4) bond length is 1.24 Å. The C(7)-O(5) bond length is 1.25 Å. There are two inequivalent N sites. In the first N site, N(1) is bonded in a distorted trigonal planar geometry to one Er(1), one C(2), and one C(6) atom. In the second N site, N(2) is bonded in a bent 120 degrees geometry to one C(3) and one C(5) atom. H(1) is bonded in a single-bond geometry to one C(5) atom. There are five inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Er(1) and one C(4) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Er(1) and one C(1) atom. In the third O site, O(3) is bonded in a single-bond geometry to one C(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to one Er(1) and one C(7) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Er(1) and one C(7) atom. Linkers: 4 [O]C(=O)c1cnc(C([O])=O)c(C([O])=O)n1. Metal clusters: 4 [Er]. The MOF has largest included sphere 3.98 A, density 2.33 g/cm3, surface area 2221.63 m2/g, accessible volume 0.11 cm3/g