The synthesis and characterization of 15 ternary microporous layered tin(IV) thioselenide, TMA(2)Sn(3)S(x)Se(7-x), materials (where 0 less than or equal to x less than or equal to 7), enabled the chalcogenide distribution in the framework to be defined. The structure of the materials is based upon the apex and edge connection of three trigonal bipramidal SnSySe5-y building blocks (where 0 less than or equal to y less than or equal to 5) into a broken-cube cluster. Six of these clusters are linked together into a planar honeycomb layer arrangement of hexagonally shaped 24-atom rings that an stacked together in a parallel manner to form the microporous layered lattice. An understanding of the chalcogenide distribution necessitated a combination of powder X-ray diffraction (PXRD), and UV-vis diffuse-reflectance, FT-Raman, and H-1/Sn-119 CP/MAS NMR spectroscopies. PXRD established the arrangement of chalcogenides in the porous layers, UV-vis diffuse-reflectance spectroscopy determined the organization at the level of the clusters, while FT-Raman and NMR spectroscopies elucidated the local distribution around the trigonal bipyramids. By investigation of the TMA(2)Sn(3)S(x)Se(7-x) structure at these different length scales, it was found that the chalcogenide distribution is statistical at the global level of the unit cell but displays site selectivity at the local level of the trigonal bipyramids.