光控有机笼封装钯纳米粒子:硝基苯衍生物催化还原

Photocontrollable Organic Cage Encapsulated Palladium Nanoparticles: Catalytic Reduction of Nitrobenzene Derivatives

摘要

多孔有机笼具有内部孔道结构和稳定的芳香族骨架，同时具有多个钯结合位点，可调控钯纳米粒子的合成。近年来，不同类型的有机笼被用来构建催化反应的纳米粒子，但基于光控单元构建的有机笼被用于催化反应的案例仍然鲜有报道。本文利用含醛基的二噻吩乙烯体系与环己二胺发生动态亚胺化学反应，构筑出稳定的光控有机笼 POC-1, 随后 POC-1 封装金属纳米粒子钯形成纳米催化剂。通过电子显微镜对光控有机笼封装的钯纳米粒子进行表征，结果表明纳米催化剂被成功包裹进分子笼空腔内；通过紫外可见光谱系统比较纳米粒子对硝基芳烃还原的催化性能，表明开环态笼子是闭环态笼子的 4 倍；通过原位光照实验表明，催化反应活性差异是由开/闭环体钯的负载量不同导致的，且负载量与开/闭环体分子笼的空腔大小有关。

Abstract

Porous organic cages possess an internal cavity and stable aromatic backbones with multiple palladium binding sites, which are suitable for controlled synthesis and stabilization of palladium nanoparticles. In recent years, various types of porous organic cages have been employed to construct nanoparticles for catalytic reactions. However, few organic cages constructed by photoresponsive units have been used to control catalytic reactions by photo irradiation. Herein, stable photo-controllable organic cages of POC-1 are constructed from dithienylethene with aldehyde and cyclohexanediamine through dynamic imine chemistry, showing a typical [3+6] molecular configuration. The metal nanoparticles of palladium are encapsulated by the organic cages as nanocatalysts, which are characterized by high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) and Cryo-Transmission Electron Microscopy (cryo-TEM). Through the TEM analysis, it can be concluded that 2.5 nm Pd nanoparticles could be stabilized in open form organic cages, while 2.0 nm Pd nanoparticles could be encapsulated in closed-form cages. As compared with the catalytic reduction of nitroaromatics by ultraviolet-visible spectroscopy (UV-Vis), the catalytic rate of Pd@ o-POC-1 is about four times higher than that of Pd@ c-POC-1.In-situ illumination experiments demonstrates that catalytic reaction activity is significantly associated with the varying loading amounts of palladium in the open/closed cages，which might be related to the size of the cavity of open and closed forms. Compared to the closed form, the open form exhibits higher catalytic reduction performance due to its higher palladium loading. This study provides a novel idea for utilizing photo-controlled organic cages encapsulating nanoparticles in catalytic reactions, offering broad application prospects.

关键词

光开关 / 多孔有机笼 / 钯纳米粒子 / 硝基苯衍生物 / 催化还原反应

Key words

photoswitch / porous organic cage / palladium nanoparticle / nitrobenzene derivative / catalytic reduction reaction

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基金资助

国家自然科学基金重点项目(22338006)