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通过DNP-SENS和快速MAS确定分子和表面位的结构

Amrit Venkatesh^1,2, Alicia Lund³, Lukas Rochlitz⁴

¹Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States.

Journal of the American Chemical Society

|October 22, 2020

概括

在分子层面描述异质催化剂是很困难的. 这项研究使用先进的核磁共振技术来分析二氧化上高度分散的位,证实了明确的单位结构.

科学领域:

催化剂
材料科学
光谱学

背景情况:

由于表面度较低,在分子水平上对异质催化剂的表征具有挑战性.
现有的技术难以选择性地探测异质材料的表面.
了解高度分散的活性位点的结构对于催化剂设计至关重要.

研究的目的:

开发和应用先进的核磁共振技术,用于在二氧化上高度分散的 (Pt) 位点的分子级别特征.
通过表面有机金属化学来确认Pt物种的单位或单原子性质.
确定这些孤立的Pt位点的结构和电子特性.

主要方法:

在快速魔角旋转 (MAS) 条件下使用室温质子检测核磁共振 (NMR) 光谱.
动态核极化表面增强NMR光谱 (DNP-SENS) 以获得195Pt固态NMR光谱.
实施双极HMQC和S-REDOR实验以确定195Pt同位移和Pt-H距离.

主要成果:

成功获得了 (SiO) 上高度分散的Pt位点的195个固态NMR光谱.
H{195Pt}双极-HMQC提供了195Pt同位移,而S-REDOR则产生了Pt-H距离.
对DNP增强的195Pt光谱的分析允许确定195Pt化学转移张量参数.
核磁共振数据提供了强有力的证据,表明孤立的Pt位点具有明确的单位结构.

结论:

快速MAS NMR和DNP-SENS的联合使用对于在异质催化剂中的低度,高度分散的金属位点的特征是有效的.
表面有机金属方法产生具有单位结构的明确隔离的Pt位点.
这种方法提升了对异质催化剂的分子层面理解,为改善催化剂设计铺平了道路.

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