TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preparation (Claimed): Preparation of (I) comprises: mixing a nitrogen-containing aromatic ring compound as the nitrogen source and a transition metal compound as the coordination metal source; pyrolyzing the resultant mixture in an inert gas atmosphere; etching the resultant pyrolyzed product in a strong acid; and filtering, washing, and drying the pyrolyzed product after the etching. Preferred Components: The nitrogen-containing aromatic ring compound: comprises 1,10-phenanthroline and/or a 1,10-phenanthroline derivative; and is a calcined product. The coordination metal source comprises transition metal oxalate, transition metal oxide, transition metal sulfate, transition metal nitrate, transition metal hydroxide, transition metal halide and/or transition metal carbonate. The transition metal comprises iron, nickel, cobalt, zinc, copper, manganese and/or palladium. The equivalent ratio of the nitrogen source to the coordination metal source is 4 or smaller. Preferred Method: The step of mixing the nitrogen source and the coordination metal source: is carried out by crushing and/or milling; and comprises further mixing a pore forming agent, which comprises iron oxalate, cobalt oxalate, iron oxide and/or copper oxide. The method comprises, following the step of etching, heat treating the pyrolyzed product in a nitrogen/hydrogen mixture gas atmosphere (second heat treatment); etching a second heat treated product obtained by the second heat treatment step in a strong acid (second etching step); and heat treating the second time heated product after the second etching step in nitrogen gas atmosphere (third heat treatment). EXAMPLE - Phenanthroline and milled iron oxalate were mixed and heat treated in an inert gas atmosphere e.g. nitrogen (450 degrees C for 1 hour, 750 degrees C for 30 minutes). After cooling, etched in 1 N hydrochloric acid for 12 hours. After filtering and washing, vacuum-dried to give a phenanthroline/iron oxalate catalyst.