Keggin型多酸负载的单原子催化剂(M1/POM,M = Ni,Pd, Pt,Cu, Ag,Au, POM = [PW12O40]3-)活化氮气分子的密度泛函理论计算研究

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)(M₁/POM (M = Ni, Pd, Pt, Cu, Ag, Au, POM = PW₁₂O₄₀]^3-)的分子几何、电子结构及红外光谱进行计算。结果表明，Pt₁/POM对N₂分子具有潜在的活化能力，Pt₁/POM与N₂相互作用主要来自于由金属Pt的d_xz和d_yz轨道与N₂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―O_c―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。

DFT Study of POM-Supported Single Atom Catalyst (M1/POM,M = Ni,Pd, Pt,Cu, Ag,Au, POM = [PW12O40]3-) for Activation of Nitrogen Molecules

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 = PW₁₂O₄₀]^3-) have been studied based on density factional theory (DFT) combined with natural bond orbital (NBO) analysis method. The results show that Pt₁/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_xz and d_yz orbital of Pt atom and the π* 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.