To enhance the sorptive property of carbon dioxide and to recover carbon dioxide efficiently.

A gas adsorbing material 10 is composed of a stacked unit wherein a plurality of monomers 20 provided with four complex nuclear metals 22 (for example, Zn) combined in a tetrahedron shape by oxygen, and a plurality of monocarboxylic acids 24 that are coordinated in the complex nuclear metals 22 so as to have interaction parts 25 (e.g., benzene ring) stacked with other structures by uncombined interaction and to surround the complex nuclear metals 22. When an adsorption gas (carbon dioxide) is present, the gas adsorbing material 10 undergoes phase transition to a structure having spaces each of which is larger in molecular size than the gas, so as to incorporate the adsorbed gas. When the pressure of adsorbed gas is further increased, it undergoes even greater structural phase transition to a structure capable of incorporating a larger amount of the adsorbed gas. The gas adsorbing material 10 undergoes such structural phase transition reversibly, so that it can achieve adsorption and desorption of carbon dioxide while exerting a high adsorption amount compared with methane, nitrogen, steam, or the like.