Precise Control of Cu Nanoparticle Size and Catalytic Activity through Pore Templating in Zr Metal-Organic Frameworks
Precise Control of Cu Nanoparticle Size and Catalytic Activity through Pore Templating in Zr Metal-Organic Frameworks
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DOI：
10.1021/acs.chemmater.0c00059
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发表时间：
2020-04-14
影响因子：
8.6
通讯作者：
Farha, Omar K.
中科院分区：
文献类型：
--
作者：
Mian, Mohammad Rasel;Redfern, Louis R.;Farha, Omar K.
由金属有机框架 (MOF) 内的纳米颗粒组成的复合材料将纳米技术的广泛功能与晶体支架的结构规律相结合。尽管如此，利用 MOF 孔径的可调性来控制这些复合材料中的纳米颗粒直径和空间排列仍然是一个巨大的挑战。在这里，我们提出了两种基于 Zr 的 MOF，NU-901 和 NU-907，它们具有不同的孔径，可作为不同尺寸（分别类似于 1.5 nm 和类似于 0.9 nm）的 Cu 纳米粒子（CuNP）的受控生长的模板。原位同步加速器 X 射线散射和衍射实验，以及对分布函数和差异包络密度分析，为了解每个 MOF 孔中这些 CuNP 的尺寸和位置提供了重要的见解。这些复合材料（表示为 CuNPs@NU-901 和 CuNPsp NU-907）被证明是乙炔选择性加氢成乙烯的有效催化剂，具有清晰的结构-性能关系，表明较大的 CuNPs 比较小的颗粒表现出更高的活性。使用过渡态能量的密度泛函理论计算进一步探讨了这种违反直觉的趋势，以了解 CuNP 结构对催化功能的作用。计算表明，有限尺寸的铜簇的半氢化活化能高于铜表面的活化能。这项工作展示了 MOF 孔内模板化纳米颗粒生长作为实现复合材料结构和功能精确控制的一般策略的效用。
Composite materials composed of nanoparticles trapped within metal-organic frameworks (MOFs) combine the broad functionality of nanotechnology with the structural regularity of crystalline scaffolds. Still, leveraging the tunability of MOF pore sizes to control nanoparticle diameter and spatial arrangement in these composites remains a great challenge. Here we present two Zr-based MOFs, NU-901 and NU-907, with distinct pore diameters that serve as templates for the controlled growth of Cu nanoparticles (CuNPs) of different sizes (similar to 1.5 nm and similar to 0.9 nm, respectively). In situ synchrotron X-ray scattering and diffraction experiments, along with pair distribution function and difference envelope density analyses, provide crucial insight into the size and location of these CuNPs in the pores of each MOF. These composites (denoted as CuNPs@NU-901 and CuNPsp NU-907) are shown to be competent catalysts for the selective hydrogenation of acetylene to ethylene, with a clear structure-property relationship indicating that larger CuNPs exhibit higher activity than smaller particles. This counterintuitive trend is further explored using density functional theory calculations of transition state energies to understand the role of CuNP structure on catalytic functionality. The calculations show that the activation energy for semihydrogenation is higher for a Cu cluster of finite size than for a Cu surface. This work demonstrates the utility of templated nanoparticle growth within MOF pores as a general strategy to achieve precise control over the composite structure and functionality.