The decomposition of NO catalysed by Cu pairs coordinated at the Al-substituted T3 sites of the 10-membered rings of Cu-ZSM-5 was studied by means of DFT/ONIOM calculations. Three mechanisms for NO decomposition were defined on the active site, all based on the formation and further decomposition of an hyponitrite anion, which gives the NO molecule and a [Cu‒O‒Cu] bridge, where both copper ions are oxidized. NO can react with the oxidized active site according to two different spin-allowed mechanisms which give immediately the products, N + O. Otherwise, NO reacts with a new reduced site according to a spin-forbidden mechanism which gives N and a second [Cu‒O‒Cu] bridge. When the latter mechanism occurs, reduced sites are restored by further reaction of [Cu‒O‒Cu] with NO and desorption of NO, which is finally decomposed on a second [Cu‒O‒Cu] site, giving O + NO. Turnover frequencies (TOFs) calculated by means of the Energetic Span model showed that one of the spin-allowed mechanisms should be relatively fast, whereas the spin-forbidden one is expected to be extremely slow. Computational results were discussed with reference to experimental data available in the literature.

中文翻译：

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Cu-ZSM-5 作为 NO 分解催化剂的 DFT 研究：位于 T3 四面体位点的 Cu(I) 对的可能活性

通过DFT/ONIOM计算研究了Cu-ZSM-5十元环Al取代T3位点配位的Cu对催化NO的分解。在活性位点上定义了 NO 分解的三种机制，全部基于次亚硝酸根阴离子的形成和进一步分解，产生 NO 分子和 [Cu-O-Cu] 桥，其中两个铜离子都被氧化。 NO 可以根据两种不同的自旋允许机制与氧化活性位点反应，立即生成产物 N + O。否则，NO 根据自旋禁止机制与新的还原位点反应，生成 N 和第二个 [Cu -O-Cu]桥。当后一种机制发生时，还原位点通过[Cu-O-Cu]与NO的进一步反应和NO的解吸而恢复，最终在第二个[Cu-O-Cu]位点上分解，得到O + NO。通过能量跨度模型计算的周转频率（TOF）表明，一种允许自旋的机制应该相对较快，而禁止自旋的机制预计会非常慢。参考文献中的实验数据讨论了计算结果。