利用超高场固态 NMR 揭示无定形硅铝酸盐中 Brønsted 酸性桥联 SiOHAl 基团。
Revealing Brønsted Acidic Bridging SiOHAl Groups on Amorphous Silica-Alumina by Ultrahigh Field Solid-State NMR.
机构信息
Laboratory for Catalysis Engineering, School of Chemical and Biomolecular Engineering, The University of Sydney, Sydney, New South Wales 2006, Australia.
Department of Engineering, Macquarie University, Sydney, New South Wales 2109, Australia.
出版信息
J Phys Chem Lett. 2021 Dec 2;12(47):11563-11572. doi: 10.1021/acs.jpclett.1c02975. Epub 2021 Nov 22.
Amorphous silica-aluminas (ASAs) are important acidic catalysts and supports for many industrially essential and sustainable processes. The identification of surface acid sites with their local structures on ASAs is of critical importance for tuning their catalytic properties but still remains a great challenge and is under debate. Here, ultrahigh magnetic field (35.2 T) Al-{H} D-HMQC (dipolar-mediated heteronuclear multiple-quantum correlation) two-dimensional NMR experiments demonstrate two types of Brønsted acid sites in ASA catalysts. In addition to the known pseudobridging silanol acid sites, the use of ultrahigh field NMR provides the first direct experimental evidence for the existence of bridging silanol (BS: SiOHAl) acid sites in ASAs, which has been hotly debated in the past few decades. This discovery provides new opportunities for scientists and engineers to develop and apply ASAs in various reaction processes due to the significance of BS in chemical and fuel productions based on its strong Brønsted acidity.
无定形硅铝酸盐（ASAs）是许多工业必需和可持续过程中的重要酸性催化剂和载体。确定 ASAs 表面酸位及其局部结构对于调整其催化性能至关重要，但仍然是一个巨大的挑战，并且存在争议。在这里，超高磁场（35.2 T）Al-{H} D-HMQC（偶极介导的异核多量子相关）二维 NMR 实验证明了 ASA 催化剂中有两种类型的 Brønsted 酸位。除了已知的拟桥接硅醇酸位外，超高场 NMR 的使用还为 ASAs 中桥接硅醇（BS：SiOHAl）酸位的存在提供了首个直接实验证据，这在过去几十年中一直是激烈争论的话题。这一发现为科学家和工程师在各种反应过程中开发和应用 ASAs 提供了新的机会，因为 BS 在基于其强 Brønsted 酸性的化学和燃料生产中的重要性。
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