CaHgC9N3H9S2O7 crystallizes in the monoclinic P2_1/c space group. Ca(1) is bonded in a 8-coordinate geometry to one N(2), one O(5), one O(6), one O(7), two equivalent O(3), and two equivalent O(4) atoms. The Ca(1)-N(2) bond length is 2.52 Å. The Ca(1)-O(5) bond length is 2.54 Å. The Ca(1)-O(6) bond length is 2.42 Å. The Ca(1)-O(7) bond length is 2.45 Å. There is one shorter (2.33 Å) and one longer (2.56 Å) Ca(1)-O(3) bond length. There is one shorter (2.33 Å) and one longer (2.62 Å) Ca(1)-O(4) bond length. Hg(1) is bonded in a 5-coordinate geometry to one N(1), one S(1), two equivalent S(2), and one O(1) atom. The Hg(1)-N(1) bond length is 2.24 Å. The Hg(1)-S(1) bond length is 2.44 Å. There is one shorter (2.93 Å) and one longer (2.97 Å) Hg(1)-S(2) bond length. The Hg(1)-O(1) bond length is 2.53 Å. There are nine inequivalent C sites. In the first C site, C(1) is bonded in a distorted bent 120 degrees geometry to one C(3), one O(1), and one O(2) atom. The C(1)-C(3) bond length is 1.52 Å. The C(1)-O(1) bond length is 1.27 Å. The C(1)-O(2) bond length is 1.26 Å. In the second C site, C(2) is bonded in a distorted bent 120 degrees geometry to one C(4), one O(3), and one O(4) atom. The C(2)-C(4) bond length is 1.49 Å. The C(2)-O(3) bond length is 1.27 Å. The C(2)-O(4) bond length is 1.26 Å. In the third C site, C(3) is bonded in a distorted trigonal planar geometry to one C(1), one C(4), and one N(1) atom. The C(3)-C(4) bond length is 1.40 Å. The C(3)-N(1) bond length is 1.35 Å. In the fourth C site, C(4) is bonded in a trigonal planar geometry to one C(2), one C(3), and one C(5) atom. The C(4)-C(5) bond length is 1.40 Å. In the fifth C site, C(5) is bonded in a distorted single-bond geometry to one C(4) and one H(7) atom. The C(5)-H(7) bond length is 1.09 Å. In the sixth C site, C(6) is bonded in a distorted single-bond geometry to one C(7) and one H(8) atom. The C(6)-C(7) bond length is 1.39 Å. The C(6)-H(8) bond length is 1.09 Å. In the seventh C site, C(7) is bonded in a distorted trigonal planar geometry to one C(6), one N(1), and one H(9) atom. The C(7)-N(1) bond length is 1.34 Å. The C(7)-H(9) bond length is 1.09 Å. In the eighth C site, C(8) is bonded in a distorted linear geometry to one N(2) and one S(1) atom. The C(8)-N(2) bond length is 1.17 Å. The C(8)-S(1) bond length is 1.66 Å. In the ninth C site, C(9) is bonded in a linear geometry to one N(3) and one S(2) atom. The C(9)-N(3) bond length is 1.18 Å. The C(9)-S(2) bond length is 1.64 Å. There are three inequivalent N sites. In the first N site, N(1) is bonded in a trigonal planar geometry to one Hg(1), one C(3), and one C(7) atom. In the second N site, N(2) is bonded in a distorted linear geometry to one Ca(1) and one C(8) atom. In the third N site, N(3) is bonded in a single-bond geometry to one C(9) atom. There are nine inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(5) atom. The H(1)-O(5) bond length is 1.00 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(5) atom. The H(2)-O(5) bond length is 0.98 Å. In the third H site, H(3) is bonded in a single-bond geometry to one O(6) atom. The H(3)-O(6) bond length is 0.99 Å. In the fourth H site, H(4) is bonded in a single-bond geometry to one O(6) atom. The H(4)-O(6) bond length is 0.97 Å. In the fifth H site, H(5) is bonded in a single-bond geometry to one O(7) atom. The H(5)-O(7) bond length is 0.99 Å. In the sixth H site, H(6) is bonded in a single-bond geometry to one O(7) atom. The H(6)-O(7) bond length is 0.99 Å. In the seventh H site, H(7) is bonded in a single-bond geometry to one C(5) atom. In the eighth H site, H(8) is bonded in a single-bond geometry to one C(6) atom. In the ninth H site, H(9) is bonded in a single-bond geometry to one C(7) atom. There are two inequivalent S sites. In the first S site, S(1) is bonded in an L-shaped geometry to one Hg(1) and one C(8) atom. In the second S site, S(2) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Hg(1) and one C(9) atom. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Hg(1) and one C(1) atom. In the second O site, O(2) is bonded in a single-bond geometry to one C(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Ca(1) and one C(2) atom. In the fourth O site, O(4) is bonded in a 1-coordinate geometry to two equivalent Ca(1) and one C(2) atom. In the fifth O site, O(5) is bonded in a water-like geometry to one Ca(1), one H(1), and one H(2) atom. In the sixth O site, O(6) is bonded in a distorted water-like geometry to one Ca(1), one H(3), and one H(4) atom. In the seventh O site, O(7) is bonded in a distorted water-like geometry to one Ca(1), one H(5), and one H(6) atom. Linkers: 4 [O]C(=O)c1cccnc1C([O])=O. Metal clusters: 4 [Ca] ,4 [Hg]. The MOF has largest included sphere 2.50 A, density 2.41 g/cm3, surface area 2970.54 m2/g, accessible volume 0.08 cm3/g