Ravi Manoj, Sushkevich Vitaly L, van Bokhoven Jeroen A
Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland.
Laboratory for Catalysis and Sustainable Chemistry, Paul Scherrer Institute, Villigen, Switzerland.
Nat Mater. 2020 Oct;19(10):1047-1056. doi: 10.1038/s41563-020-0751-3. Epub 2020 Sep 21.
Zeolites are a class of materials that are of great relevance for industrial catalysis. Several fundamental questions relating to the structure and role of the Lewis acid sites in these materials remain unanswered. Proposals for the origin of such species can broadly be classified into three categories, which have distinct structures: extra-framework, framework-associated and framework aluminium. In this Perspective, we review each of these proposals and proceed to analyse their suitability to understand experimental results. Contrary to traditional belief, the number of Lewis acid sites does not always correlate to extra-framework aluminium content. As a result, we highlight that the terms 'extra-framework' and 'framework-associated' aluminium should be used with caution. We propose how the usage of different characterization techniques can enable the closure of knowledge gaps concerning the strength, multiplicity, localization and structure of catalytically active Lewis acid sites in zeolites.
沸石是一类对工业催化具有重大意义的材料。关于这些材料中路易斯酸位点的结构和作用，有几个基本问题仍未得到解答。关于此类物种起源的提议大致可分为三类，它们具有不同的结构：骨架外、骨架相关和骨架铝。在这篇观点文章中，我们回顾了这些提议中的每一个，并进而分析它们对理解实验结果的适用性。与传统观念相反，路易斯酸位点的数量并不总是与骨架外铝含量相关。因此，我们强调应谨慎使用“骨架外”和“骨架相关”铝这两个术语。我们提出，如何使用不同的表征技术能够填补关于沸石中催化活性路易斯酸位点的强度、多重性、定位和结构方面的知识空白。
