Abstract:
Ammonia (NH3) is industrially produced from dinitrogen (N2) and dihydrogen (H2) by the Haber-Bosch process, although H2 is prepared from fossil fuels, and the reaction requires harsh conditions. On the other hand, microorganisms have fixed nitrogen under ambient reaction conditions. Recently, well-defined molecular transition metal complexes have been found to work as catalyst to convert N2 into NH3 by reactions with chemical reductants and proton sources under ambient reaction conditions. Among them, involvement of both N2-splitting pathway and proton-coupled electron transfer is found to be very effective for high catalytic activity. Furthermore, direct electrocatalytic and photocatalytic conversions of N2 into NH3 have been recently achieved. In addition to catalytic formation of NH3, selective catalytic conversion of N2 into hydrazine (NH2NH2) and catalytic silylation of N2 into silylamines have been reported. Catalytic C-N bond formation has been more recently established to afford cyanate anion (NCO-) under ambient reaction conditions. Further development of direct conversion of N2 into nitrogen-containing compounds as well as green ammonia synthesis leading to the use of ammonia as an energy carrier is expected.
摘要:
氨(NH3)是通过Haber-Bosch工艺从二氮(N2)和二氢(H2)工业生产的,尽管H2是由化石燃料制备的,反应需要苛刻的条件。另一方面,微生物在环境反应条件下具有固定的氮。最近,已经发现明确定义的分子过渡金属络合物作为催化剂,通过在环境反应条件下与化学还原剂和质子源反应将N2转化为NH3。其中,发现N2分裂途径和质子耦合电子转移的参与对于高催化活性非常有效。此外,最近已经实现了N2到NH3的直接电催化和光催化转化。除了催化形成NH3之外,已经报道了将N2选择性催化转化为肼(NH2NH2)和将N2催化甲硅烷基化为甲硅烷基胺。最近已经建立了催化C-N键形成以在环境反应条件下提供氰酸酯阴离子(NCO-)。预计将N2直接转化为含氮化合物以及绿色氨合成的进一步发展,从而将氨用作能量载体。