TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The gaseous mixture further comprises nitrogen, helium, hydrogen and/or argon, and water. The flow rate of gaseous mixture is 40-60 mL/minute. When the gaseous mixture is heated to 20-30 degrees C, the conversion rate of carbon monoxide to carbon dioxide is 90-100 or 80% or more, and when the gaseous mixture is heated to 0-10 degrees C, the conversion rate of carbon monoxide to carbon dioxide is 40-50%. Water is water vapor or moisture. The content of carbon monoxide contained in the gaseous mixture is 1-10 vol.%. Manganese salt is chosen from manganese nitrate, manganese chloride, manganese bromide, manganese fluoride, manganese phosphate and manganese sulfate. Palladium compound is disodium tetrachloropalladate, dihydrogen tetrachloropalladate(II), potassium tetrachloropalladate(II), ammonium tetrachloropalladate(II), palladium(II) acetate, palladium nitrate and/or palladium sulfate. The reducing agent is hydrazine, sodium borohydride and/or potassium borohydride. The precipitate is isolated by removing the precipitate from the reaction mixture by centrifugation, filtration, distillation and/or decantation, then washing the precipitate, and drying the precipitate. Preferred Properties: Manganese(II,III) oxide has an average pore diameter of 1-50 nm. The mesoporous support has an average pore volume of 0.2-1 cm/g and an average BET surface area of 60-150 m2/g. Preferred Component: The reactor is a fixed-bed tubular reactor.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: Solvent is ethanol, propanol, ether, acetone, ethyl acetate, water and/or dimethylformamide.    TECHNOLOGY FOCUS - POLYMERS - Preferred Process: Manganese(II,III) oxide is prepared by mixing triblock copolymer, manganese salt and solvent for 30 minutes to 2 hours to form a solution, evaporating the solution by heating at 50-80 degrees C for 24-96 hours, and calcining obtained product at 300-600 degrees C for 30 minutes to 6 hours. Preferred Components: Triblock copolymer is poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol), poly(ethyleneimine)-poly(ethylene glycol)- poly(ethyleneimine), poly(ethylene glycol)-polyacetal-poly(ethylene glycol) and/or polyacetal-poly(ethylene glycol)-polyacetal