The problem of providing a metal complex having excellent gas adsorption performance, gas storage performance, and gas separation performance is solved by a metal complex comprising a dicarboxylic acid compound (I) including 20 to 99 mole % of a dicarboxylic acid compound (I-1) selected from terephthalic acid derivatives having an electron-donating group in the 2nd position such as 2-methoxyterephthalic acid, 2-methylterephthalic acid, and terephthalic acid, and 80 to 1 mole % of a dicarboxylic acid compound (I-2) selected from terephthalic acid derivatives having an electron-withdrawing group in the 2nd position such as 2-nitroterephthalic acid, 2-fluoroterephthalic acid, 2-chloroterephthalic acid, 2-bromoterephthalic acid, and 2-iodoterephthalic acid; at least one kind of metal ion selected from metal ions belonging to Group 2 and Groups 7 to 12 of the periodic table; and an organic ligand capable of bidentate binding to the metal ion.
