第三族金属氧化物离子对二氧化碳转化的红外光谱研究

Infrared Spectroscopy of CO2 Transformation by Group Ⅲ Metal Monoxide Cations

本文利用红外光解离光谱研究了第三族金属氧化物离子对二氧化碳分子的转化机制.研究表明,对于[ScO(CO2)n]^+体系,在n≤4时,形成了溶剂化结构;在n=5时,形成了碳酸盐结构,实现了二氧化碳的转化.对于[YO(CO2)n]^+体系,需要4个二氧化碳分子就可以实现二氧化碳的转化.而在[YO(CO2)n]^+体系中,只发现了溶剂化结构,没有观察到碳酸盐结构.理论计算表明,[YO(CO2)n]^+体系拥有最小的溶剂化结构向碳酸盐结构转化能垒,[LaO(CO2)n]^+体系拥有最大的溶剂化结构向碳酸盐结构转化能垒.本文从分子水平揭示了不同金属氧化物离子对二氧化碳分子转化的影响规律.

Infrared photodissociation spectroscopy of mass-selected[MO(CO2)n]^+(M=Sc,Y,La)complexes indicates that the conversion from the solvated structure into carbonate one can be achieved by the ScO^+ cation at n=5 and by the YO^+ cation at n=4,while only the solvated structures are observed for the LaO^+ cation.These findings suggest that both the ScO^+ and YO^+cations are able to fix CO2 into carbonate.Quantum chemical calculations are performed on[MO(CO2)n]^+ to identify the structures of the low-lying isomers and to assign the observed spectral features.Theoretical analyses show that the[YO(CO2)n]^+ complex has the smallest barrier for the conversion from the solvated structure into carbonate one,while[LaO(CO2)n]^+ exhibits the largest conversion barrier among the three metal oxide cations.The present system affords a model in clarifying the effect of different metals in catalytic CO2 transformation at the molecular level.