Hydrothermal reactions of Cd(NO3)2 and NaH2SIP (5‐sulfoisophthalic acid monosodium salt) at pH = 2 and 7 produce [Cd2(μ2‐OH2)2(HSIP)2(H2O)6] (1) and [Cd5(μ2‐OH)2(μ3‐OH)2(SIP)2(H2O)5]n (2), respectively. A similar hydrothermal reaction in the presence of dpp [1,3‐bis(4‐pyridyl)propane] yields {[Cd3(SIP)2(dpp)6]·4(H2O)}n (3). Single‐crystal X‐ray diffraction reveals that compound 1 has a discrete dinuclear structure with the [Cd2(μ2‐OH2)2] unit. Polymer 2 features an inorganic layer, which has centrosymmetric 12‐ and 24‐membered rings composed of chair‐shaped [Cd4(μ3‐OH)2] units and Cd(μ2‐OH)2(CO2) units, and is interconnected by SIP into a 3D framework. Complex 3 contains a 1D ladder‐like [Cd4(SIP)4]n unit with four cadmium atoms co‐planar, which is interconnected by dpp into a 2D nanosized layered structure. In the solid state, compounds 1 and 3 exhibit blue‐violet photoluminescence with maxima at 436 and 409 nm upon excitation at 342 and 350 nm, respectively. However, compound 2 shows photoluminescence with the maximum at 306 nm upon excitation at 270 nm.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)