Existence of dual species composed of Cu(+) in CuMFI being bridged by C(2)H(2).
Existence of dual species composed of Cu(+) in CuMFI being bridged by C(2)H(2).
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DOI：
10.1039/c000967a
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发表时间：
2010-06
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通讯作者：
Atsushi Itadani;T. Yumura;T. Ohkubo;Hisayoshi Kobayashi;Y. Kuroda
中科院分区：
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作者：
Atsushi Itadani;T. Yumura;T. Ohkubo;Hisayoshi Kobayashi;Y. Kuroda
研究了乙炔（C（2）H（2））和二氧化碳（CO（2））与铜离子交换的MFI沸石（CuMFI）在室温下的相互作用。发现CuMFI优先吸附C（2）H（2），而该材料不响应CO（2）。为了阐明CuMFI的特异性，采用了各种实验技术和理论计算的组合。在CuMFI上C（2）H（2）吸附的初始阶段，明显观察到140和110 kJ mol（-1）的相互作用能，表明存在两种类型的吸附C（2）H（2）。在1620和1814 cm（-1）处出现两个明显的红外吸收带，这两个吸收带归属于C（2）H（2）的C[三键]C伸缩振动模式，它们的吸附态不同。光致发光和X射线吸收光谱表明，CuMFI中的亚铜离子（Cu（+））作为一个显着的C（2）H（2）吸附的有效网站。从后者的光谱分析和基于密度泛函理论的计算结果，双Cu（+）的形成。（C（2）H（2））. Cu（+）络合物是首次在CuMFI中被发现的，这种特殊的Cu（+）位构型是导致C（2）H（2）极强吸附的原因。而在CuMFI中，CO（2）分子必须呈弯曲结构才能吸附在Cu（+）上.结果表明，CuMFI中Cu（+）对C（2）H（2）和CO（2）的吸附响应差异是由于Cu（+）的电子供给性质与相应分子的杂化轨道之间的化学作用。这一工作促进了对CuMFI中C（2）H（2）活化和N（2）固定的活性中心状态的进一步理解。
The interaction of ethyne (C(2)H(2)), as well as of carbon dioxide (CO(2)), with copper-ion-exchanged MFI zeolite (CuMFI) at room temperature was examined. It was found that CuMFI preferentially adsorbs C(2)H(2), while this material does not respond to CO(2). To clarify the specificity of CuMFI, a combination of various experimental techniques and theoretical calculations was adopted. Distinctive interaction energies of 140 and 110 kJ mol(-1) were clearly observed at the initial stage of C(2)H(2) adsorption on CuMFI, suggesting the presence of two types of adsorbed C(2)H(2). Two distinct IR bands at 1620 and 1814 cm(-1) appeared, which were assigned to the C[triple bond]C stretching vibration modes of C(2)H(2) differing in their adsorbed state. Both photoluminescence and X-ray absorption spectra showed that cuprous ions (Cu(+)) in CuMFI act as efficient sites for a marked C(2)H(2) adsorption. From the analysis of the latter spectra and the calculational results based on the density functional theory, the formation of dual Cu(+)...(C(2)H(2))...Cu(+) complexes was indicated for the first time for CuMFI, and such a special configuration of the Cu(+) sites contributed to the extremely strong adsorption of C(2)H(2). In contrast, it was necessary for the linear CO(2) molecule to take a bent structure to be adsorbed on Cu(+) in CuMFI. It was concluded that the difference in the adsorption response of Cu(+) in CuMFI towards C(2)H(2) and CO(2) is due to the chemistry between the nature of electron donation of Cu(+) and the hybrid orbitals of the respective molecules. This work promotes further understanding of the states of active centres in CuMFI for C(2)H(2) activation, as well as for N(2) fixation.