The effective generation of methanol directly from gaseous carbon dioxide has received considerable attention in recent years since it can recycle the greenhouse gas and produce a clean fuel. Herein, we report an enzymatic approach for carbon dioxide fixation using formate dehydrogenase (F_(ate)DH), formaldehyde dehydrogenase (F_(ald)DH) and alcohol dehydrogenase (ADH) co-encapsulated in a silica gel as the catalysts. The gels were prepared by a modified sol-gel process that uses tetramethoxysilane (TMOS) as the precursor and nicotinamide adenine dinucleotide (NADH) as an electron donor. The enzymatic conversion of CO_2 to methanol was carried out at low temperatures and low pressures. The effects of the reaction temperature, pH value, the amount of enzyme and the amount of NADH on the yields of methanol have been investigated. The highest yield of methanol was 92.1%. The activity of immobilized enzymes was a little lower than that of the free enzymes due to the minor conformation change of the enzyme and the existence of additional diffusion hindrance.
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