3,5‐Pyrazole­di­carboxyl­ic acid monohydrate

In the title compound, C₅H₄N₂O₄·H₂O, the 3,5‐pyrazoledicarboxylic acid (H₃pdc) molecules are joined into one‐dimensional chains by O—H?O and N—H?O hydrogen bonds, with distances of 2.671 (2) and 2.776 (2) Å, respectively. The one‐dimensional chains form a three‐dimensional structure via O—H?OW and OW—HW?N hydrogen bonds, with distances of 2.597 (3) and 2.780 (3) Å, respectively. In addition to the potential for forming open‐channel frameworks, access to the six coordination atoms of H₃pdc can be directly controlled by varying the pH of the reaction environment, allowing further control over the design and synthesis of novel coordination polymers using various metal centers.