Keggin型多酸负载的单原子催化剂(M_1/POM,M=Ni,Pd,Pt,Cu,Ag,Au,POM=[PW_(12)O_(40)]^(3-))活化氮气分子的密度泛函理论计算研究

DFT Study of POM-Supported Single Atom Catalyst(M_1/POM,M=Ni,Pd,Pt,Cu,Ag,Au,POM=[(PW_(12)O_(40)])^(3-)) for Activation of Nitrogen Molecules

采用量子化学密度泛函理论(DFT)结合自然键轨道(NBO)分析的方法对一系列以多酸为载体的单原子催化剂(SACs)(M_1/POM(M=Ni,Pd,Pt,Cu,Ag,Au,POM=[PW_(12)O_(40)]^(3-))的分子几何、电子结构及红外光谱进行计算。结果表明,Pt_1/POM对N_2分子具有潜在的活化能力,Pt_1/POM与N_2相互作用主要来自于由金属Pt的d_(xz)和d_(yz)轨道与N_2的π*反键轨道重叠,金属Pt的d^(xz)、d^(yz)轨道上的电子填充到了氮气的π*反键轨道上弱化了N≡N成键,导致了N≡N之间的键长增大,有效的活化了氮气分子。对它们红外光谱的分析表明,Keggin型多酸负载金属后W―Oc―W振动吸收峰发生劈裂,产生了五个典型的红外特征吸收峰。

Molecular geometries, electronic structure, and infrared spectroscopy of a series of polyoxometalate （POM）-supported single atom catalyst （SACs） （M1/POM （M = Ni, Pd, Pt, Cu, Ag, Au, POM = [PW12040]3-） have been studied based on density factional theory （DFT） combined with natural bond orbital （NBO） analysis method. The results show that Ptl/POM has a higher reactivity for activation of N2 relevant to the others. The interaction between the isolated Pt atom and N2 arises from an orbital mixture, which is formed by the d^z and dyz orbital of Pt atom and the E＊ anti-bond orbit of N2 molecule. The electron transfer from Pt atom to the nitrogen molecule leads to a weakened N-N bond. The N-N bond distance increases when compared with the free N2 molecule. All results indicate an effective activation of the nitrogen molecules. For DFT-derived IR spectra, the four characteristic peaks of Keggin-type POM split into five because of introduction of the isolated metal atom.