IntroductionRecently, researchers have undertaken a number of approaches towards the design and synthesis of metal–organic coordination polymers based upon the concept of crystal engineering.1–4Introduced to the design of more efficient topochemical reactions in the early 1960s by Rabinowich and Schmidt,5the concept of crystal engineering is now widely used in organic supramolecular chemistry and metal–organic coordination polymers for achieving physical and chemical targets. In 1989, the first extended metal–organic polymeric network deliberately designed and synthesized was reported.6Intense research activities in this field have recently produced many new metal–organic polymers of great diversity.1–4In recent years, the self­assembly of extended one­, two­ and three­dimensional metal–organic network polymersviahydrogen bonding has attracted much attention.7,8The utilization of hydrogen bonding is a well known design principle in the construction of supramolecular architecture and crystal engineering.9–11Our interests in exploring new coordination networks focus on the bifunctional organic ligands. Bifunctional ligands have the advantages of both sturdy covalent bonding and flexible, non­covalent bonding interactions and solubility, such as hydrogen bonds. Hydrogen bond­containing coordination polymers may have potential applications in the biomedical field and nanomaterials.12Pyridinecarboxylate ligands have shown interesting properties in the construction of coordination polymers.13,14The introduction of hydrogen bonds can be achieved by the use of coordinating water molecules: these coordinating water molecules tend to form hydrogen bonds with neighboring nitrogen­ and oxygen­containing organic units in order to link the network structures.12a,15For example, pyridine-3,5­dicarboxylate (pdc) is a good candidate for this purpose. One of the possible networks from pdc coordination to metal ions (Scheme 1) is to form a two­dimensional sheet.Under hydrothermal conditions the open­metal center inScheme 1can easily adopt water molecules at the axial positions to result in trigonal bipyramidal coordination metal centers. The coordination water molecules will probably interact with the carboxylate groups in adjacent layersviahydrogen bonds to give a three­dimensional network. Here, we report a three­dimensional network constructedviaboth projected covalent and O–H⋯O hydrogen bonding interactions: [(H2O)2Cu(pdc)]1.