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首页> 外文期刊>Nano letters >Conversion of Metal-Organic Cage to Ligand-Free Ultrasmall Noble Metal Nanocluster Catalysts Confined within Mesoporous Silica Nanoparticle Supports
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Conversion of Metal-Organic Cage to Ligand-Free Ultrasmall Noble Metal Nanocluster Catalysts Confined within Mesoporous Silica Nanoparticle Supports

机译：将金属 - 有机笼转化为非配体的超惰性金属纳米光栅催化剂，限制在中孔硅纳米粒子载体中

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Supported ultrasmall noble metal nanocluster-based (UNMN-based) catalysts are one of the most important classes of solid materials for heterogeneous catalysis. In this work, we present a novel strategy for the controlled synthesis of ligand-free UNMN nanocatalysts based on in situ reduction of a palladium-based (Pd-based) metal-organic cage (MOC) confined within monosized, thiol-modified mesoporous silica nanoparticle (MSN) supports. By taking advantage of the high mutual solubility of MOCs and MSNs in DMSO and the strong interactions between the thiol-modified MSN pore wall and MOC surface, a good dispersion of MOC molecules was achieved throughout the MSN support. The close correspondence of the MSN pore diameter (ca. 5.0 nm) with the diameter of the MOC (ca. 4.0 nm) confines MOC packing to approximately a monolayer. Based on this spatial constraint and electrostatic binding of the MOC to the thiol-modified MSN pore surface, in situ MOC reduction followed by metal atom diffusion, coalescence, and anchoring on the active sites resulted in ligand-free Pd-based UNMNs of approximately 0.9 +/- 0.2 nm in diameter decorating the MSN pore surfaces. Control experiments of the reduction of a conventional palladium source or the reduction of free, unconstrained cages in solution under the same conditions only produced large metal nanocrystals (NP, >2 nm), confirming the importance of confined reduction to achieve a highly catalytically active surface. In light of this strategy, two catalytic experiments including the reaction of 4-nitrophenol to 4-aminophenol and the Suzuki C-C coupling reaction show superior catalytic activity of the engineered MSN-supported UNMN nanocatalysts compared to their free form and state of the art commercial catalysts. We believe that our new strategy will open new avenues for artificially designed UNMN-inspired nanoarchitectures for wide applications.
机译：支持的超摩尔贵金属纳米烛蛋牙（基于UMANN的）催化剂是异构催化的最重要的固体材料之一。在这项工作中，我们基于原位还原在单倍化，硫醇改性的介孔二氧化硅内局限于贫钯（Pd基）金属 - 有机笼（MOC）的原位减少了一种基于钯（Pd基）金属 - 有机笼（MOC）的基于钯（Pd基）金属 - 有机笼（MOC）的新策略纳米粒子（MSN）支撑。通过利用MOCS和MSNS在DMSO中的高相互溶解度和硫醇改性的MSN孔隙壁和MOC表面之间的强相互作用，在整个MSN载体中实现了MOC分子的良好分散。 MSN孔径（CA.5.0nm）与MOC（CA.4.0nm）直径的紧密对应关系将MOC填料限制在大约单层中。基于MOC的这种空间约束和静电结合到硫醇改性的MSN孔表面，原位MOC还原，然后是金属原子扩散，聚结和活性位点上的锚定导致与韧带的PD基悬角中约为0.9直径+/- 0.2nm装饰MSN孔表面。在相同条件下，在溶液中减少常规钯源或减少自由，无约束笼的控制实验仅产生大金属纳米晶（NP，> 2nm），确认狭窄的减少的重要性，以实现高度催化的活性表面。鉴于该策略，包括4-硝基苯酚至4-氨基苯酚的反应和铃木CC偶联反应的两个催化实验显示了与其自由形式和现有的商业催化剂的自由形式和状态的工程化MSN支撑的联管纳米催化剂的优异催化活性。我们相信，我们的新战略将为人工设计的联管鼓励纳米建筑开辟新的途径，以实现广泛的应用。

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