NOVELTY - New (dicarboxylic acid)-metal complexes contain at least one compound selected from dicarboxylic acids having specific formula, at least one bivalent metal selected from copper, rhodium, chromium, molybdenum, palladium, zinc, and tungsten, and an organoligand of pKa of at least 4 bidentately coordinated to the metal.    USE - Present complexes are used in the gas storage technology field (claimed).    ADVANTAGE - The present complexes are useful as gas occlusion materials and are prepared simply and inexpensively. The complexes have good characteristics as gas occlusion material (high specific surface area and high pore size value) and exhibit large adsorption amount per volume and good repeat character. The gas occlusion material can store gas at pressurization state under ordinary temperature condition and can store gas at pressurization state under ordinary temperature condition. The LNG storage device stores LNG in packing tank of adsorption type, even when temperature of LNG tank rose, to keep tank pressure in allowable range.    DETAILED DESCRIPTION - New (dicarboxylic acid)-metal complexes contain at least one compound selected from dicarboxylic acids of formula (I), at least one bivalent metal selected from copper, rhodium, chromium, molybdenum, palladium, zinc, and tungsten, and an organoligand of pKa of at least 4 bidentately coordinated to the metal.    R = alkylene, alkenylene, alkynylene, optionally substituted arylene.    INDEPENDENT CLAIMS are also included for:    (A) a method of preparation of the new (dicarboxylic acid)-metal complexes;    (B) a gas occlusion material consisting of (dicarboxylic acid)-metal complex;    (C) gas occlusion material composed by pressure molding of (dicarboxylic acid)-metal complex;    (D) a method for gas storage adsorbing to store gas in which methane is main component in gas occlusion material under pressure;    (E) gas storage device equipped with inlet (5a) and outlet (5b) through which storage target gas can go in and out, keeping mechanism (6) possible to keep gas in vessel at pressurized state, and with pressure vessel (4) possible to keep ordinary temperature; here, gas occlusion material (8) is placed in (4) and storage target is gas of which main component is methane;    (F) gas motorcar equipped with gas storage device (1) and internal combustion engine (3) obtaining driving force from gas of which main component is methane supplied from (1);    (G) gas storage tank of adsorption type containing gas occlusion material; and    (H) LNG storage device composed by connecting LNG tank and packing tank of adsorption type through safety valve so that, when pressure of LNG tank increased to above prescribed value, evaporated gas of definite amount would be adsorbed to store in storage tank of adsorption type containing gas occlusion material.    DESCRIPTION OF DRAWING(S) - Figure 1 shows concept of crystal structure of (dicarboxylic acid-metal) complex.