采用密度泛函理论研究甲基噻吩在硫化钼团簇上的吸附行为

STUDY ON METHYLTHIOPHENE ADSORPTION ON MoS_2 CLUSTER BY DENSITY FUNCTIONAL THEORY

利用密度泛函理论研究了噻吩和甲基噻吩在硫化钼团簇的不饱和钼上的吸附行为,考察甲基对吸附效果的影响。结果表明:平行吸附比垂直吸附更稳定;噻吩和甲基噻吩在Mo16S32团簇上的平行吸附能力由大到小的顺序为2,3-二甲基噻吩>3-甲基噻吩>3,4-二甲基噻吩>2,4-二甲基噻吩>噻吩>2-甲基噻吩>2,5-二甲基噻吩;噻吩上含有一个甲基时,甲基位于3位有利于吸附,位于2位不利于吸附;噻吩上含有两个甲基时,吸附能力随着两个甲基间的距离增大而减小;通过键长、Mayer键级、Mulliken布局数分析可知,吸附后甲基噻吩环上C—S的键长增加、键级减弱,噻吩环上各原子杂化轨道上的电子流向Mo原子,Mo原子部分d轨道上的电子反馈到噻吩环的反键轨道,甲基噻吩得到活化,有利于后续的噻吩环加氢亲电反应。

Adsorption properties of thiophene and methylthiophenes on the unsaturated Mo site of MoSz cluster were investigated by the first-principle DFT calculations. The calculated results indicate that the thiophene compounds prefer to lie on the top two Mo atoms of Mo16 S32 cluster. The adsorption ability of thiophene compounds on the Mo16 S32 cluster is 2,3-DMT〉3-MT〉3,4-DMT〉2,4-DMT〉 TP〉2-MT〉2,5-DMT. The results indicate that thiophene with one methyl substituent in 3-position is beneficial to adsorption, but methyl in 2-position is not conducive to adsorption. When two positions on thiophene are substituted, the adsorption energy decreases as the distance of the two methyl increases. According to the bond length, Mayer bond order and Mulliken population analysis, the C--S bond length and bond order of the adsorbed thiophene is up and down, respectively after adsorption. The electrons in the hybridized orbitals of adsorbed thiophene ring transfer to Mo atoms, and the electrons in the d orbitals of Mo atom transfer to antibonding orbital of thiophene ring. It benefits for the thiophene rings activation and subsequent electrophilic hydrodesulfurization reaction.