An organometallic complex [Cu2(pyridine-3,5-dicarboxylate)2]n is provided by bonding a plurality of Cu2(pyridine-3,5-dicarboxylate)2 repeating units to each other. The organometallic complex can be obtained by the steps of dissolving copper acetate monohydrate or anhydrate and pyridine-3,5-dicarboxylic acid in a solvent, heating the solution at 50° C. to 140° C. for 24 to 168 hours to generate a reaction product, and then removing a guest molecule from the reaction product.