TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: A cross-linking ligand capable of carrying out bidentate coordination is added to salt of central metal. The carboxylate group of carboxylic acid derivative is prepared by ion exchange process. Metal salt (A) is dissolved in a solvent (I) to obtain a solution (S1). Metal salt (B) is dissolved in a solvent (II) to obtain a solution (S2). The solutions (S1,S2) are mixed to obtain porous metal complex. The metal salts are reacted by irradiating ultrasonic wave.Preferred Salt: At least one of the metal salt (A,B) is carboxylic acid metal salt. The carboxylic acid metal salt contains salt of alkali metal or alkaline earth metal. The carboxylic acid metal salt contains carboxylic acid derivative of formula: (XOOC)n1-R-(COOX')n2.R=alkylene, alkynylene, alkenylene or arylene having substituent, preferably arylene having substituent chosen from group of formula (III-XII);X=hydrogen atom, alkali metal or alkaline earth metal, preferably sodium or potassium;X'=alkali metal or alkaline earth metal, preferably sodium or potassium; andn1,n2=1-4.The carboxylic acid metal salt contains dicarboxylic acid derivative of formula: XOOC-R-COOX'. At least one of metal salts (A,B) contains metal chosen from metal group containing 2-4 valent metal. The metal of one metal salt contains bivalent metal chosen from copper, zinc, molybdenum, ruthenium, chromium, nickel and rhodium. One of the metal contains nitrate, sulfate, acetate, carbonate and/or formate. The metal salt chosen from sodium nitrate, sodium sulfate, sodium acetate, sodium carbonate, sodium formate, potassium nitrate, potassium sulfate, potassium acetate, potassium carbonate and/or potassium formate, is obtained as byproduct during reaction of metal salts (A,B).Preferred Solvent: The solvent(s) is chosen from N,N'-dimethyl formamide, N,N'-diethyl formamide, water, alcohol, tetrahydrofuran, benzene, toluene, hexane, acetone and acetonitrile, preferably N,N'-dimethyl formamide, N,N'-diethyl formamide, water, and alcohol.Preferred Property: The porous metal complex has pH of 8-10.