精确原子结构的金属簇直接催化转化甲烷制甲醇/乙醇

It is of paramount importance to attain atomically precise metal clusters and by solving their atomic structure of the clusters, one will be able to precisely correlate the catalytic properties with their exact atomic structure and to learn what control the surface activation, surface active site structure and catalytic mechanism, which ultimately is able to control the selectivity and activation of catalytic reactions. Here based on the previous results, we will further investigate the catalysis of Ni6(SR)12 cluster with double crown structure for the direct conversion of methane and oxygen into methanol/ethanol, and see whether Ni cluster can distinguish the methane and methanol/ethanol to avoid the production of by-products. We will unveil catalysis of a central gold atom through experiment coupled with theory and show the central atom bustling into and out of the gold catalyst such as non-hollow Au25 and hollow Au24 clusters accompanied by an improvement and detriment in catalytic performance of methane conversion. We will explore the origin of C-H bond activation and C-O bond formation on the atomically precise metal clusters confined into porous materials in the process of methane selective oxidation, in order to ultimately design highly active and highly selective catalysts for methane conversion. Such confined clusters with precise atom packing structure will not only provide new opportunities for unraveling catalysis at an atomic level, but also promote the exploration of methane conversion toward high value-added products.

结构精确的金属原子簇具有特定的原子空间排列结构和电子结构，对某些反应由于结构的匹配而产生特异的催化作用。本项目我们将在初期研究的基础上，深入研究“双皇冠结构”Ni6(SR)12原子簇催化甲烷和氧气反应制甲醇/乙醇的反应机制，从原子水平上揭示其处在不同空间位点的金属活性位能否对甲烷和产物分子进行识别，避免产物分子深度氧化，进而避免副产物的生成；深入研究“实心”Au25和“空心”Au24原子簇的不同原子空间排列结构所带来的活性中心的物种和数量的差异，以及它们对甲烷分子的作用不同最终影响反应的选择性和活性，并由此获知Au原子簇中原子在空间是如何排列才能成为甲烷C-H键断键和C-O键成键的活性位点;通过实验手段将获得的原子簇封装到合适的无机多孔材料中，提高其热稳定性，用于催化甲烷的选择性氧化制甲醇/乙醇。为甲烷活化和催化带来新的研究思路和方法，促进甲烷等低碳烷烃的活化和相关催化理论的发展。

甲烷作为天然气的主要成分在石油化工行业中的应用具有重要意义，但是甲烷的分子结构非常稳定，它的直接转化在热力学上是不利的。本项目针对甲烷等重要分子的催化转化反应，设计并精准制备金属团簇催化剂，解决纳米颗粒催化剂对其催化活性不足的问题。制备了Ni6(SC2H4Ph)12团簇，在可见光照条件下能够催化甲烷和氧气反应得到甲醇和甲酸，研究揭示了此镍团簇在可见光照下具有向底物与反应中间体分子中的开壳层氧原子转移电子的能力，且甲烷与可见光活化的含氧物种经过多步反应生成甲醇，甲醇与可见光活化的含氧物种反应生成甲酸。通过精准调变团簇核原子增加与减少，合成了Au25(PPh3)10(SC2H4Ph)5Cl2和Au24(PPh3)10(SC2H4Ph)5Cl2团簇，揭示了Au24团簇在催化甲烷氧化反应中发生重构转变为Au25，阐明了Au24的重构过程会降低甲氧基和氢氧根自由基物种的反应能垒，实现了Au24起始活性高于Au25。并拓展研究至金基团簇催化CO2转化反应。本项目研究为实现资源与能源小分子的精准转化提供科学指导和新型催化材料。