NOVELTY - A metal complex comprises polyhydric carboxylic acid compound, metal ion(s) including ion of group 2-13 metal, organic ligand which is coordinated in multiple positions to the metal ion, and 3-24C aliphatic monocarboxylic acid compound.    USE - Metal complex is used for adsorbent, separation material and occlusion material used for adsorbing, separating and occluding carbon dioxide, hydrogen, carbon monoxide, oxygen, nitrogen, 1-4C hydrocarbon, noble gas, hydrogen sulfide, ammonia, sulfur oxide, nitrogen oxide, siloxane and organic steam. The occlusion material is used for airtight gas-storage apparatus for gas motor vehicle (all claimed).    ADVANTAGE - The material containing the metal complex has high water resistance.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) adsorbent, which contains metal complex;    (2) occlusion material (4), which contains metal complex;    (3) airtight gas storage apparatus (1), which has pressure-resistant container (2) provided with entrance (6) and exit (5) of gas, gas occlusion space (3) inside the pressure-resistant container, and the occlusion material internally provided to the gas occlusion space;    (4) gas motor vehicle, which has internal combustion engine which obtains driving force with fuel gas supplied from the gas storage apparatus;    (5) separation material, which contains metal complex;    (6) separation method, which involves contacting the metal complex and mixed gas under pressure of 0.01-10 MPa; and    (7) manufacture of metal complex, which involves reacting polyhydric carboxylic acid compound, metal ion, organic ligand and 3-24C aliphatic monocarboxylic acid compound in solvent, and depositing obtained metal complex.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the gas motor vehicle using the metal complex.    Gas storage apparatus (1)    Pressure-resistant container (2)    Gas occlusion space (3)    Occlusion material (4)    Exit (5)    Entrance (6)