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dwma

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[资源] Angew. Chem. Int. Ed.---催化转化CO2

二氧化碳是重要的温室气体。许多工业过程以及汽车废气都要排放CO2.对CO2的催化反应处理，一种将其还原直接转变成燃料；另一种是将其功能化，以进一步用于合成其他化合物。这篇文章提出了一种结合二者的新方法。
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Carbon dioxide is a nontoxic, abundant C1 building block,” says Cantat. “Only a handful of processes using this starting material have been developed, because carbon dioxide is a very stable molecule that can not easily be made to react.” To date, there have been two different approaches for the use of carbon dioxide. According to Cantat, “In the ‘vertical’ approach, the carbon dioxide is reduced, which means that the oxidation state of the carbon atom is reduced by the formal replacement of oxygen with hydrogen. This results in molecules such as methanol or formic acid, which can be converted into fuels.” These products have a higher energy content than carbon dioxide, but only a handful of chemicals can be produced this way.
“In the ‘horizontal’ approach, the carbon atom is functionalized, which means that it forms new bonds to oxygen, nitrogen, or other carbon atoms”, continues Cantat. “The oxidation state stays the same, the energy content is not increased.” This does not produce fuels, but chemicals that are useful building blocks for chemical syntheses, such as urea.
The French team thus tried a compromise approach, a combination of both methods to make a “diagonal” approach. By their method, the carbon dioxide is both reduced and functionalized in one step. This allows the synthesis of a much greater number of chemicals, directly from CO2.
This reaction requires three things: a reducing agent (e.g. a silane), an organic molecule to be attached to the carbon atom of the carbon dioxide (e.g. an amine), and a special catalyst that catalyzes both the reduction and the functionalization. The successful catalyst is a special organic base consisting of a nitrogen-containing ring system. “Variation of the reaction partners should allow us to make a whole series of chemical compounds that are normally obtained from petrochemical feedstocks,” says Cantat, “for example, formamide derivatives, which are important intermediates for both chemical and pharmaceutical industries.”
Figure . Approaches to recycling transformations of CO2 as alternatives

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