A new building block containing an imidazolium salt was synthesized and used for the construction of supramolecular networks with metal ions. We discovered the concomitant formation of the N-heterocyclic carbene-copper complex (CN = 2) in the self-assembly of imidazolium dicarboxylates and copper nitrates in N,N-dimethylformamide under heating. The proton in the 2 position of the imidazolium salt was abstracted, and Cu-II was reduced to Cu-I during the self-assembly process.