Spontaneous self-assembly of Et3Sn+-, nBu4N+- and [Cu(CN)4]3- ions in H2O affords white, crystalline [(nBu4N)(ET3Sn)2-Cu(CN)4]infinity (7). A single-crystal X-ray study has confirmed the formation of a negatively charged, three-dimensional host framework with wide and parallel, interior channels occupied by well-ordered nBu4N+ guest cations. 7: Tetragonal I-lattice, I4(3)22; a, b = 14.360(2), c = 40.003(6) angstrom; cell volume = 8249(2) angstrom3, Z = 8; wR2 = 0.1145; wR2' (all data) = 0.1355. The title compound has, moreover, been characterized by IR/Raman (nu(CN)) and MAS solid-state NMR spectroscopy (C-13, Sn-119). The NMR features are consistent with requirements based on the asymmetric unit. Even modest variations of the organic groups belonging to the 3D-framework, and of the template, R4N+, respectively, have been shown to afford 'derailed' assemblies of distinctly different stoichiometries, and/or spectroscopic properties, from [(R4N)(R'3Sn)2Cu(CN)4].