Ni(HCOO)2 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(1), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form a mixture of edge and corner-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 64-66°. The Ni(1)-O(1) bond length is 2.04 Å. The Ni(1)-O(3) bond length is 2.06 Å. The Ni(1)-O(4) bond length is 2.08 Å. The Ni(1)-O(5) bond length is 2.08 Å. The Ni(1)-O(6) bond length is 2.05 Å. The Ni(1)-O(7) bond length is 2.02 Å. In the second Ni site, Ni(2) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(8) atom to form edge-sharing NiO6 octahedra. The Ni(2)-O(2) bond length is 2.01 Å. The Ni(2)-O(3) bond length is 2.07 Å. The Ni(2)-O(4) bond length is 2.06 Å. The Ni(2)-O(5) bond length is 2.08 Å. The Ni(2)-O(6) bond length is 2.04 Å. The Ni(2)-O(8) bond length is 2.02 Å. In the third Ni site, Ni(3) is bonded to two equivalent O(10), two equivalent O(7), and two equivalent O(9) atoms to form corner-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles are 64°. Both Ni(3)-O(10) bond lengths are 2.03 Å. Both Ni(3)-O(7) bond lengths are 2.10 Å. Both Ni(3)-O(9) bond lengths are 2.05 Å. In the fourth Ni site, Ni(4) is bonded to two equivalent O(1), two equivalent O(11), and two equivalent O(12) atoms to form corner-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles are 66°. Both Ni(4)-O(1) bond lengths are 2.08 Å. Both Ni(4)-O(11) bond lengths are 2.04 Å. Both Ni(4)-O(12) bond lengths are 2.03 Å. There are six inequivalent C sites. In the first C site, C(1) is bonded in a trigonal planar geometry to one H(1), one O(1), and one O(2) atom. The C(1)-H(1) bond length is 0.93 Å. The C(1)-O(1) bond length is 1.27 Å. The C(1)-O(2) bond length is 1.23 Å. In the second C site, C(2) is bonded in a trigonal planar geometry to one H(2), one O(10), and one O(4) atom. The C(2)-H(2) bond length is 0.93 Å. The C(2)-O(10) bond length is 1.24 Å. The C(2)-O(4) bond length is 1.27 Å. In the third C site, C(3) is bonded in a trigonal planar geometry to one H(3), one O(11), and one O(5) atom. The C(3)-H(3) bond length is 0.93 Å. The C(3)-O(11) bond length is 1.22 Å. The C(3)-O(5) bond length is 1.26 Å. In the fourth C site, C(4) is bonded in a trigonal planar geometry to one H(4), one O(3), and one O(8) atom. The C(4)-H(4) bond length is 0.93 Å. The C(4)-O(3) bond length is 1.27 Å. The C(4)-O(8) bond length is 1.24 Å. In the fifth C site, C(5) is bonded in a trigonal planar geometry to one H(5), one O(12), and one O(7) atom. The C(5)-H(5) bond length is 0.93 Å. The C(5)-O(12) bond length is 1.23 Å. The C(5)-O(7) bond length is 1.28 Å. In the sixth C site, C(6) is bonded in a trigonal planar geometry to one H(6), one O(6), and one O(9) atom. The C(6)-H(6) bond length is 0.93 Å. The C(6)-O(6) bond length is 1.26 Å. The C(6)-O(9) bond length is 1.23 Å. There are six inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one C(1) atom. In the second H site, H(2) is bonded in a single-bond geometry to one C(2) atom. In the third H site, H(3) is bonded in a single-bond geometry to one C(3) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one C(4) atom. In the fifth H site, H(5) is bonded in a single-bond geometry to one C(5) atom. In the sixth H site, H(6) is bonded in a single-bond geometry to one C(6) atom. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Ni(1), one Ni(4), and one C(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Ni(2) and one C(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one C(4) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one C(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one C(3) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one C(6) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Ni(1), one Ni(3), and one C(5) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Ni(2) and one C(4) atom. In the ninth O site, O(9) is bonded in a distorted bent 120 degrees geometry to one Ni(3) and one C(6) atom. In the tenth O site, O(10) is bonded in a distorted bent 120 degrees geometry to one Ni(3) and one C(2) atom. In the eleventh O site, O(11) is bonded in a distorted bent 120 degrees geometry to one Ni(4) and one C(3) atom. In the twelfth O site, O(12) is bonded in a distorted bent 150 degrees geometry to one Ni(4) and one C(5) atom. Linkers: 24 [O]C=O. Metal clusters: 12 [Ni]. The MOF has largest included sphere 4.68 A, density 1.89 g/cm3, surface area 2753.27 m2/g, accessible volume 0.22 cm3/g