[OBJECT] To provide a metal-organic framework having high hygroscopicity under low humidity conditions, and a method for producing such a metal-organic framework.
[SOLVING MEANS] A method for producing a coordinatively unsaturated metal-organic framework includes the steps of providing a precursor metal-organic framework comprising a metal cluster and a polycarboxylic acid ion and a monocarboxylic acid ion coordinated to the metal cluster, and allowing the precursor metal-organic framework and a metal salt having a Lewis acidity to coexist in a solvent to desorb at least a part of the monocarboxylic acid ion, which is coordinated to the metal cluster, from the metal cluster, as well as a coordinatively unsaturated metal-organic framework, including an M6O8-x(OH)x-type metal cluster and carboxylic acid ions including a polycarboxylic acid ion as a polydentate ligand and a C1-3 monocarboxylic acid ion as a monodentate ligand coordinated to the metal cluster.