当前位置: X-MOL 学术J. Am. Chem. Soc. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
The Structure of Molecular and Surface Platinum Sites Determined by DNP-SENS and Fast MAS 195Pt Solid-State NMR Spectroscopy
Journal of the American Chemical Society ( IF 15.0 ) Pub Date : 2020-10-22 , DOI: 10.1021/jacs.0c09101
Amrit Venkatesh 1, 2 , Alicia Lund 3 , Lukas Rochlitz 4 , Ribal Jabbour 3 , Christopher P. Gordon 4 , Georges Menzildjian 3 , Jasmine Viger-Gravel 3, 5 , Pierrick Berruyer 6 , David Gajan 3 , Christophe Copéret 4 , Anne Lesage 3 , Aaron J. Rossini 1, 2
Affiliation  

The molecular level characterization of heterogeneous catalysts is challenging due to the low concentration of surface sites and the lack of techniques that can selectively probe the surface of a heterogeneous material. Here, we report the joint application of room temperature proton-detected NMR spectroscopy under fast magic angle spinning (MAS) and dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP-SENS), to obtain the 195Pt solid-state NMR spectra of a prototypical example of highly dispersed Pt sites (single site or single atom), here prepared via surface organometallic chemistry, by grafting [(COD)Pt(OSi(OtBu)3)2] (1, COD = 1,5-cyclooctadiene) on partially dehydroxylated silica (1@SiO2). Compound 1@SiO2 has a Pt loading of 3.7 wt %, a surface area of 200 m2/g, and a surface Pt density of around 0.6 Pt site/nm2. Fast MAS 1H{195Pt} dipolar-HMQC and S-REDOR experiments were implemented on both the molecular precursor 1 and on the surface complex 1@SiO2, providing access to 195Pt isotropic shifts and Pt-H distances, respectively. For 1@SiO2, the measured isotropic shift and width of the shift distribution constrain fits of the static wide-line DNP-enhanced 195Pt spectrum, allowing the 195Pt chemical shift tensor parameters to be determined. Overall the NMR data provide evidence for a well-defined, single-site structure of the isolated Pt sites.

中文翻译:

通过 DNP-SENS 和快速 MAS 195Pt 固态核磁共振光谱测定的分子和表面铂位点的结构

由于表面位点浓度低以及缺乏可以选择性探测非均相材料表面的技术,多相催化剂的分子水平表征具有挑战性。在这里,我们报告了在快速魔角旋转 (MAS) 和动态核极化表面增强 NMR 光谱 (DNP-SENS) 下室温质子检测 NMR 光谱的联合应用,以获得原型示例的 195Pt 固态 NMR 光谱高度分散的 Pt 位点(单位点或单原子),这里通过表面有机金属化学制备,通过在部分脱羟基上接枝 [(COD)Pt(OSi(OtBu)3)2] (1, COD = 1,5-环辛二烯)二氧化硅(1@SiO2)。化合物 1@SiO2 的 Pt 负载量为 3.7 wt%,表面积为 200 m2/g,表面 Pt 密度约为 0.6 Pt 位点/nm2。快速 MAS 1H{195Pt} 偶极-HMQC 和 S-REDOR 实验在分子前体 1 和表面复合物 1@SiO2 上实施,分别提供了 195Pt 各向同性位移和 Pt-H 距离。对于 1@SiO2,测得的各向同性位移和位移分布宽度约束静态宽线 DNP 增强 195Pt 光谱,允许确定 195Pt 化学位移张量参数。总体而言,NMR 数据为分离的 Pt 位点的明确定义的单位点结构提供了证据。静态宽线 DNP 增强 195Pt 光谱的测量各向同性位移和位移分布约束拟合的宽度,允许确定 195Pt 化学位移张量参数。总体而言,NMR 数据为分离的 Pt 位点的明确定义的单位点结构提供了证据。静态宽线 DNP 增强 195Pt 光谱的测量各向同性位移和位移分布约束拟合的宽度,允许确定 195Pt 化学位移张量参数。总的来说,NMR 数据为分离的 Pt 位点的明确定义的单位点结构提供了证据。
更新日期:2020-10-22
down
wechat
bug