Molecular metal complexes on supports have drawn wide attention as catalysts offering new properties and opportunities for precise synthesis to make uniform catalytic species that can be understood in depth. Here we highlight advances in research with catalysts that are a step more complex than those incorporating single, isolated metal atoms on supports. These more complex catalysts consist of supported noble metal clusters and supported metal oxide clusters, and our emphasis is placed on some of the simplest and best-defined of these catalysts, made by precise synthesis, usually with organometallic precursors. Characterization of these catalysts by spectroscopic, microscopic, and theoretical methods is leading to rapid progress in fundamental understanding of catalyst structure and function, and to expansion of this class of materials. The simplest supported metal clusters incorporate two metal atoms each—they are pair-site catalysts. These and clusters containing several metal atoms have reactivities determined by the metal nuclearity, the ligands on the metal, and the supports, which themselves are ligands. Metal oxide clusters are also included in the discussion presented here, with Zr₆O₈ clusters that are nodes in metal–organic frameworks being among those that are understood the best. The surface and catalytic chemistries of these metal oxide clusters are distinct from those of bulk zirconia. A challenge in using any supported cluster catalysts is associated with their possible sintering, and recent research shows how metal nanoparticles can be encapsulated in sheaths with well-defined porous structures—zeolites—that make them highly resistant to sintering.

中文翻译：

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合成的负载型簇状催化剂体积小，简单，选择性好且稳定

载体上的分子金属络合物作为催化剂提供了新的性能，并提供了精确合成的机会，以制造出可以被深入理解的均匀催化物种，因此受到了广泛的关注。在这里，我们重点介绍使用催化剂的研究进展，该过程比在载体上掺入单个孤立金属原子的催化剂要复杂得多。这些更复杂的催化剂由负载的贵金属簇和负载的金属氧化物簇组成，我们的重点放在这些催化剂中一些最简单和定义最明确的催化剂上，这些催化剂通常是通过有机金属前体通过精确合成制备的。通过光谱，微观和理论方法对这些催化剂进行表征，将导致对催化剂结构和功能的基本了解迅速发展，并导致此类材料的扩展。最简单的负载型金属簇各自包含两个金属原子-它们是对位催化剂。这些和含有几个金属原子的簇具有由金属核，金属上的配体和载体本身决定的反应性，所述载体本身是配体。金属氧化物团簇也包括在此处的讨论中，其中Zr在金属有机框架中作为节点的₆ O ₈簇是最能理解的簇。这些金属氧化物簇的表面和催化化学与本体氧化锆不同。使用任何负载型簇状催化剂的挑战在于其可能的烧结，最近的研究表明，如何将金属纳米颗粒封装在具有明确多孔结构（沸石）的护套中，使其具有很高的抗烧结性。