Interactions of supramolecular assemblies constructed from calixarenes or thiacalixarenes and their derivatives with single metal coordination are well studied. But we report here the assembly of p-sulfonatothiacalix[4]arene with two different alkali metals, Na and K, which has been characterized crystallographically. The X-ray crystal structure of Na₂K₄[p-sulfonatothiacalix[4]arene]·7H₂O (5) showed direct evidence for several fascinating interactions in supramolecular chemistry. We also investigated the CO₂ gas adsorption properties of complex 5.