ErH3(CO)6 crystallizes in the triclinic P1 space group. There are two inequivalent Er sites. In the first Er site, Er(1,3,4) is bonded in a distorted pentagonal pyramidal geometry to one O(1), one O(2), one O(22), one O(23), one O(3), and one O(6) atom. The Er(1,3,4)-O(1) bond length is 2.40 Å. The Er(1,3,4)-O(2) bond length is 2.47 Å. The Er(1,3,4)-O(22) bond length is 2.35 Å. The Er(1,3,4)-O(23) bond length is 2.27 Å. The Er(1,3,4)-O(3) bond length is 2.20 Å. The Er(1,3,4)-O(6) bond length is 2.30 Å. In the second Er site, Er(2) is bonded in a distorted pentagonal pyramidal geometry to one O(12), one O(16), one O(17), one O(7), one O(8), and one O(9) atom. The Er(2)-O(12) bond length is 2.30 Å. The Er(2)-O(16) bond length is 2.35 Å. The Er(2)-O(17) bond length is 2.27 Å. The Er(2)-O(7) bond length is 2.40 Å. The Er(2)-O(8) bond length is 2.47 Å. The Er(2)-O(9) bond length is 2.20 Å. There are sixteen inequivalent C sites. In the first C site, C(1,13) is bonded in a bent 120 degrees geometry to one C(2,14); one O(1); and one O(2) atom. The C(1,13)-C(2,14) bond length is 1.48 Å. The C(1,13)-O(1) bond length is 1.27 Å. The C(1,13)-O(2) bond length is 1.24 Å. In the second C site, C(2,14) is bonded in a distorted trigonal planar geometry to one C(1,13); one C(2,14); and one H(1,7) atom. The C(2,14)-C(2,14) bond length is 1.36 Å. The C(2,14)-H(1,7) bond length is 1.14 Å. In the third C site, C(3,9,21) is bonded in a distorted bent 120 degrees geometry to one C(4,22); one O(3); and one O(4) atom. The C(3,9,21)-C(4,22) bond length is 1.51 Å. The C(3,9,21)-O(3) bond length is 1.27 Å. The C(3,9,21)-O(4) bond length is 1.25 Å. In the fourth C site, C(4,22) is bonded in a distorted trigonal planar geometry to one C(3,9,21); one C(5,11,23); and one H(2,5,11) atom. The C(4,22)-C(5,11,23) bond length is 1.32 Å. The C(4,22)-H(2,5,11) bond length is 1.14 Å. In the fifth C site, C(5,11,23) is bonded in a distorted trigonal planar geometry to one C(4,22); one C(6,24); and one H(3,12) atom. The C(5,11,23)-C(6,24) bond length is 1.48 Å. The C(5,11,23)-H(3,12) bond length is 1.14 Å. In the sixth C site, C(6,24) is bonded in a bent 120 degrees geometry to one C(5,11,23); one O(5); and one O(6) atom. The C(6,24)-O(5) bond length is 1.26 Å. The C(6,24)-O(6) bond length is 1.26 Å. In the seventh C site, C(7) is bonded in a bent 120 degrees geometry to one C(8), one O(7), and one O(8) atom. The C(7)-C(8) bond length is 1.48 Å. The C(7)-O(7) bond length is 1.27 Å. The C(7)-O(8) bond length is 1.24 Å. In the eighth C site, C(8) is bonded in a distorted trigonal planar geometry to one C(20), one C(7), and one H(4) atom. The C(8)-C(20) bond length is 1.36 Å. The C(8)-H(4) bond length is 1.14 Å. In the ninth C site, C(10) is bonded in a distorted trigonal planar geometry to one C(3,9,21); one C(5,11,23); and one H(2,5,11) atom. The C(10)-C(3,9,21) bond length is 1.51 Å. The C(10)-C(5,11,23) bond length is 1.32 Å. The C(10)-H(2,5,11) bond length is 1.14 Å. In the tenth C site, C(12) is bonded in a bent 120 degrees geometry to one C(17), one O(11), and one O(12) atom. The C(12)-C(17) bond length is 1.48 Å. The C(12)-O(11) bond length is 1.26 Å. The C(12)-O(12) bond length is 1.26 Å. In the eleventh C site, C(15) is bonded in a distorted bent 120 degrees geometry to one C(16), one O(15), and one O(16) atom. The C(15)-C(16) bond length is 1.51 Å. The C(15)-O(15) bond length is 1.27 Å. The C(15)-O(16) bond length is 1.25 Å. In the twelfth C site, C(16) is bonded in a distorted trigonal planar geometry to one C(15), one C(17), and one H(8) atom. The C(16)-C(17) bond length is 1.32 Å. The C(16)-H(8) bond length is 1.14 Å. In the thirteenth C site, C(17) is bonded in a distorted trigonal planar geometry to one C(12), one C(16), and one H(9) atom. The C(17)-H(9) bond length is 1.14 Å. In the fourteenth C site, C(18) is bonded in a bent 120 degrees geometry to one C(5,11,23); one O(17); and one O(18) atom. The C(18)-C(5,11,23) bond length is 1.48 Å. The C(18)-O(17) bond length is 1.26 Å. The C(18)-O(18) bond length is 1.26 Å. In the fifteenth C site, C(19) is bonded in a bent 120 degrees geometry to one C(20), one O(19), and one O(20) atom. The C(19)-C(20) bond length is 1.48 Å. The C(19)-O(19) bond length is 1.27 Å. The C(19)-O(20) bond length is 1.24 Å. In the sixteenth C site, C(20) is bonded in a distorted trigonal planar geometry to one C(19), one C(8), and one H(10) atom. The C(20)-H(10) bond length is 1.14 Å. There are eight inequivalent H sites. In the first H site, H(1,7) is bonded in a single-bond geometry to one C(2,14) atom. In the second H site, H(2,5,11) is bonded in a single-bond geometry to one C(4,22) atom. In the third H site, H(3,12) is bonded in a single-bond geometry to one C(5,11,23) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one C(8) atom. In the fifth H site, H(6) is bonded in a single-bond geometry to one C(5,11,23) atom. The H(6)-C(5,11,23) bond length is 1.14 Å. In the sixth H site, H(8) is bonded in a single-bond geometry to one C(16) atom. In the seventh H site, H(9) is bonded in a single-bond geometry to one C(17) atom. In the eighth H site, H(10) is bonded in a single-bond geometry to one C(20) atom. There are twenty-four inequivalent O sites. In the first O site, O(1) is bonded in a distorted L-shaped geometry to one Er(1,3,4) and one C(1,13) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Er(1,3,4) and one C(1,13) atom. In the third O site, O(3) is bonded in a linear geometry to one Er(1,3,4) and one C(3,9,21) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Er(1,3,4) and one C(3,9,21) atom. The O(4)-Er(1,3,4) bond length is 2.35 Å. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Er(1,3,4) and one C(6,24) atom. The O(5)-Er(1,3,4) bond length is 2.27 Å. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Er(1,3,4) and one C(6,24) atom. In the seventh O site, O(7) is bonded in a distorted L-shaped geometry to one Er(2) and one C(7) atom. In the eighth O site, O(8) is bonded in a distorted single-bond geometry to one Er(2) and one C(7) atom. In the ninth O site, O(9) is bonded in a linear geometry to one Er(2) and one C(3,9,21) atom. The O(9)-C(3,9,21) bond length is 1.27 Å. In the tenth O site, O(10) is bonded in a bent 120 degrees geometry to one Er(1,3,4) and one C(3,9,21) atom. The O(10)-Er(1,3,4) bond length is 2.35 Å. The O(10)-C(3,9,21) bond length is 1.25 Å. In the eleventh O site, O(11) is bonded in a distorted bent 150 degrees geometry to one Er(1,3,4) and one C(12) atom. The O(11)-Er(1,3,4) bond length is 2.27 Å. In the twelfth O site, O(12) is bonded in a distorted bent 150 degrees geometry to one Er(2) and one C(12) atom. In the thirteenth O site, O(13) is bonded in a distorted L-shaped geometry to one Er(1,3,4) and one C(1,13) atom. The O(13)-Er(1,3,4) bond length is 2.40 Å. The O(13)-C(1,13) bond length is 1.27 Å. In the fourteenth O site, O(14) is bonded in a distorted single-bond geometry to one Er(1,3,4) and one C(1,13) atom. The O(14)-Er(1,3,4) bond length is 2.47 Å. The O(14)-C(1,13) bond length is 1.24 Å. In the fifteenth O site, O(15) is bonded in a linear geometry to one Er(1,3,4) and one C(15) atom. The O(15)-Er(1,3,4) bond length is 2.20 Å. In the sixteenth O site, O(16) is bonded in a bent 120 degrees geometry to one Er(2) and one C(15) atom. In the seventeenth O site, O(17) is bonded in a distorted bent 150 degrees geometry to one Er(2) and one C(18) atom. In the eighteenth O site, O(18) is bonded in a distorted bent 150 degrees geometry to one Er(1,3,4) and one C(18) atom. The O(18)-Er(1,3,4) bond length is 2.30 Å. In the nineteenth O site, O(19) is bonded in a distorted L-shaped geometry to one Er(1,3,4) and one C(19) atom. The O(19)-Er(1,3,4) bond length is 2.40 Å. In the twentieth O site, O(20) is bonded in a distorted single-bond geometry to one Er(1,3,4) and one C(19) atom. The O(20)-Er(1,3,4) bond length is 2.47 Å. In the twenty-first O site, O(21) is bonded in a linear geometry to one Er(1,3,4) and one C(3,9,21) atom. The O(21)-Er(1,3,4) bond length is 2.20 Å. The O(21)-C(3,9,21) bond length is 1.27 Å. In the twenty-second O site, O(22) is bonded in a bent 120 degrees geometry to one Er(1,3,4) and one C(3,9,21) atom. The O(22)-C(3,9,21) bond length is 1.25 Å. In the twenty-third O site, O(23) is bonded in a distorted bent 150 degrees geometry to one Er(1,3,4) and one C(6,24) atom. The O(23)-C(6,24) bond length is 1.26 Å. In the twenty-fourth O site, O(24) is bonded in a distorted bent 150 degrees geometry to one Er(1,3,4) and one C(6,24) atom. The O(24)-Er(1,3,4) bond length is 2.30 Å. The O(24)-C(6,24) bond length is 1.26 Å. Linkers: 6 [O]C(=O)/C=C/C([O])=O. Metal clusters: 4 [Er]. The MOF has largest included sphere 5.00 A, density 1.71 g/cm3, surface area 2593.03 m2/g, accessible volume 0.26 cm3/g