Na4C21S3O17 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(10), one O(14), one O(15), one O(3), one O(4), and one O(5) atom to form distorted face-sharing NaO6 octahedra. The Na(1)-O(10) bond length is 2.31 Å. The Na(1)-O(14) bond length is 2.51 Å. The Na(1)-O(15) bond length is 2.46 Å. The Na(1)-O(3) bond length is 2.54 Å. The Na(1)-O(4) bond length is 2.52 Å. The Na(1)-O(5) bond length is 2.38 Å. In the second Na site, Na(2) is bonded to one O(10), one O(14), one O(15), one O(17), and one O(6) atom to form distorted NaO5 square pyramids that share  a cornercorner with one Na(3)O5 square pyramid and  a faceface with one Na(1)O6 octahedra. The Na(2)-O(10) bond length is 2.47 Å. The Na(2)-O(14) bond length is 2.43 Å. The Na(2)-O(15) bond length is 2.47 Å. The Na(2)-O(17) bond length is 2.54 Å. The Na(2)-O(6) bond length is 2.31 Å. In the third Na site, Na(3) is bonded to one O(16), one O(17), one O(2), and two equivalent O(13) atoms to form a mixture of edge and corner-sharing NaO5 square pyramids. The Na(3)-O(16) bond length is 2.50 Å. The Na(3)-O(17) bond length is 2.39 Å. The Na(3)-O(2) bond length is 2.45 Å. There is one shorter (2.44 Å) and one longer (2.45 Å) Na(3)-O(13) bond length. In the fourth Na site, Na(4) is bonded in a 4-coordinate geometry to one O(11), one O(12), one O(16), and one O(3) atom. The Na(4)-O(11) bond length is 2.55 Å. The Na(4)-O(12) bond length is 2.97 Å. The Na(4)-O(16) bond length is 2.36 Å. The Na(4)-O(3) bond length is 2.46 Å. There are twenty-one inequivalent C sites. In the first C site, C(1) is bonded in a distorted single-bond geometry to one C(2), one C(6), and one O(1) atom. The C(1)-C(2) bond length is 1.41 Å. The C(1)-C(6) bond length is 1.39 Å. The C(1)-O(1) bond length is 1.36 Å. In the second C site, C(2) is bonded in a trigonal planar geometry to one C(1), one C(21), and one C(3) atom. The C(2)-C(21) bond length is 1.52 Å. The C(2)-C(3) bond length is 1.38 Å. In the third C site, C(3) is bonded in a bent 120 degrees geometry to one C(2) and one C(4) atom. The C(3)-C(4) bond length is 1.38 Å. In the fourth C site, C(4) is bonded in a trigonal planar geometry to one C(3), one C(5), and one S(1) atom. The C(4)-C(5) bond length is 1.42 Å. The C(4)-S(1) bond length is 1.74 Å. In the fifth C site, C(5) is bonded in a bent 120 degrees geometry to one C(4) and one C(6) atom. The C(5)-C(6) bond length is 1.37 Å. In the sixth C site, C(6) is bonded in a trigonal planar geometry to one C(1), one C(5), and one C(7) atom. The C(6)-C(7) bond length is 1.53 Å. In the seventh C site, C(7) is bonded in a water-like geometry to one C(6) and one C(9) atom. The C(7)-C(9) bond length is 1.56 Å. In the eighth C site, C(8) is bonded in a distorted single-bond geometry to one C(13), one C(9), and one O(5) atom. The C(8)-C(13) bond length is 1.45 Å. The C(8)-C(9) bond length is 1.36 Å. The C(8)-O(5) bond length is 1.36 Å. In the ninth C site, C(9) is bonded in a trigonal planar geometry to one C(10), one C(7), and one C(8) atom. The C(9)-C(10) bond length is 1.40 Å. In the tenth C site, C(10) is bonded in a bent 120 degrees geometry to one C(11) and one C(9) atom. The C(10)-C(11) bond length is 1.41 Å. In the eleventh C site, C(11) is bonded in a trigonal planar geometry to one C(10), one C(12), and one S(2) atom. The C(11)-C(12) bond length is 1.35 Å. The C(11)-S(2) bond length is 1.76 Å. In the twelfth C site, C(12) is bonded in a bent 120 degrees geometry to one C(11) and one C(13) atom. The C(12)-C(13) bond length is 1.38 Å. In the thirteenth C site, C(13) is bonded in a trigonal planar geometry to one C(12), one C(14), and one C(8) atom. The C(13)-C(14) bond length is 1.49 Å. In the fourteenth C site, C(14) is bonded in a bent 120 degrees geometry to one C(13) and one C(16) atom. The C(14)-C(16) bond length is 1.52 Å. In the fifteenth C site, C(15) is bonded in a distorted single-bond geometry to one C(16), one C(20), and one O(9) atom. The C(15)-C(16) bond length is 1.44 Å. The C(15)-C(20) bond length is 1.37 Å. The C(15)-O(9) bond length is 1.36 Å. In the sixteenth C site, C(16) is bonded in a trigonal planar geometry to one C(14), one C(15), and one C(17) atom. The C(16)-C(17) bond length is 1.39 Å. In the seventeenth C site, C(17) is bonded in a bent 120 degrees geometry to one C(16) and one C(18) atom. The C(17)-C(18) bond length is 1.37 Å. In the eighteenth C site, C(18) is bonded in a trigonal planar geometry to one C(17), one C(19), and one S(3) atom. The C(18)-C(19) bond length is 1.42 Å. The C(18)-S(3) bond length is 1.75 Å. In the nineteenth C site, C(19) is bonded in a bent 120 degrees geometry to one C(18) and one C(20) atom. The C(19)-C(20) bond length is 1.39 Å. In the twentieth C site, C(20) is bonded in a trigonal planar geometry to one C(15), one C(19), and one C(21) atom. The C(20)-C(21) bond length is 1.52 Å. In the twenty-first C site, C(21) is bonded in a bent 120 degrees geometry to one C(2) and one C(20) atom. There are three inequivalent S sites. In the first S site, S(1) is bonded in a distorted trigonal non-coplanar geometry to one C(4), one O(2), one O(3), and one O(4) atom. The S(1)-O(2) bond length is 1.45 Å. The S(1)-O(3) bond length is 1.44 Å. The S(1)-O(4) bond length is 1.48 Å. In the second S site, S(2) is bonded in a distorted trigonal non-coplanar geometry to one C(11), one O(6), one O(7), and one O(8) atom. The S(2)-O(6) bond length is 1.42 Å. The S(2)-O(7) bond length is 1.46 Å. The S(2)-O(8) bond length is 1.46 Å. In the third S site, S(3) is bonded in a distorted trigonal non-coplanar geometry to one C(18), one O(10), one O(11), and one O(12) atom. The S(3)-O(10) bond length is 1.45 Å. The S(3)-O(11) bond length is 1.44 Å. The S(3)-O(12) bond length is 1.44 Å. There are seventeen inequivalent O sites. In the first O site, O(17) is bonded in a bent 120 degrees geometry to one Na(2) and one Na(3) atom. In the second O site, O(1) is bonded in a single-bond geometry to one C(1) atom. In the third O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Na(3) and one S(1) atom. In the fourth O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Na(4), and one S(1) atom. In the fifth O site, O(4) is bonded in a distorted L-shaped geometry to one Na(1) and one S(1) atom. In the sixth O site, O(5) is bonded in a bent 150 degrees geometry to one Na(1) and one C(8) atom. In the seventh O site, O(6) is bonded in a bent 150 degrees geometry to one Na(2) and one S(2) atom. In the eighth O site, O(7) is bonded in a single-bond geometry to one S(2) atom. In the ninth O site, O(8) is bonded in a single-bond geometry to one S(2) atom. In the tenth O site, O(9) is bonded in a single-bond geometry to one C(15) atom. In the eleventh O site, O(10) is bonded in a 3-coordinate geometry to one Na(1), one Na(2), and one S(3) atom. In the twelfth O site, O(11) is bonded in a distorted single-bond geometry to one Na(4) and one S(3) atom. In the thirteenth O site, O(12) is bonded in a single-bond geometry to one Na(4) and one S(3) atom. In the fourteenth O site, O(13) is bonded in an L-shaped geometry to two equivalent Na(3) atoms. In the fifteenth O site, O(14) is bonded in an L-shaped geometry to one Na(1) and one Na(2) atom. In the sixteenth O site, O(15) is bonded in an L-shaped geometry to one Na(1) and one Na(2) atom. In the seventeenth O site, O(16) is bonded in a bent 120 degrees geometry to one Na(3) and one Na(4) atom. Linkers: 2 [O]c1c2[c]c(S([O])([O])[O])[c]c1[C]c1[c]c(S([O])([O])[O])[c]c(c1[O])[C]c1[c]c(S([O])([O])[O])[c]c(c1[O])[C]c1[c]c(S([O])([O])[O])[c]c(c1[O])[C]c1[c]c(S([O])([O])[O])[c]c(c1[O])[C]c1[c]c(S([O])([O])[O])[c]c(c1[O])[C]2 ,2 [O]c1c2[c][c][c]c1[C]c1[c]c(S([O])([O])[O])[c]c(c1[O])[C]c1[c]c(S([O])([O])[O])[c]c(c1[O])[C]c1[c]c(S([O])([O])[O])[c]c(c1[O])[C]c1[c]c(S([O])([O])[O])[c]c(c1[O])[C]c1[c]c(S([O])([O])[O])[c]c(c1[O])[C]2. Metal clusters: 16 [Na]. The MOF has largest included sphere 4.19 A, density 1.37 g/cm3, surface area 4055.14 m2/g, accessible volume 0.23 cm3/g