The simple and easy-to-prepare bifunctional molecule 2,5-dimercapto-1,4-benzenedicarboxylic acid (H₄DMBD) interacts with the increasingly harder metal ions of Cu⁺, Pb²⁺ and Eu³⁺ to form the coordination networks of Cu₆(DMBD)₃(en)₄(Hen)₆ (1), Pb₂(DMBD)(en)₂ (2) and Eu₂(H₂DMBD)₃(DEF)₄ (3), where the carboxyl and thiol groups bind with distinct preference to the hard and soft metal ions, respectively. Notably, 1 features uncoordinated carboxylate groups and Cu₃ cluster units integrated via the thiolate groups into an extended network with significant interaction between the metal centers and the organic molecules; 2 features a 2D coordination net based on the mercapto and carboxylic groups all bonded to the Pb²⁺ ions; 3 features free-standing thiol groups inside the channels of a metal-carboxylate-based network. This study illustrates the rich solid state structural features and potential functions offered by the carboxyl-thiol combination.