Zhang Jing-Zheng, Zhang Yi-Bao, Chai Hui-Li, Luo Hui-Ling, Du Chen-Xia, Huang Ren-Wu, Zang Shuang-Quan
Henan Key Laboratory of Crystalline Molecular Functional Materials, and College of Chemistry, Zhengzhou University, Zhengzhou, 450001, China.
Angew Chem Int Ed Engl. 2025 Jan 2;64(1):e202413418. doi: 10.1002/anie.202413418. Epub 2024 Oct 31.
The selective synthesis of valuable azo- and azoxyaromatic chemicals via transfer coupling of nitroaromatic compounds has been achieved by fine-tuning the catalyst structure. Here, a direct method to modulate nitrobenzene reduction and selectively alter the product from azobenzene to azoxybenzene by employing the size effect of Au is reported. Au nanoclusters (NCs) with smaller sizes embedded in ZIF-8 controllably converted nitrobenzene into azoxybenzene, while supported Au nanoparticles (NPs) selectively catalyzed nitrobenzene reduction to azobenzene. X-ray photoelectron spectroscopy (XPS) and Diffuse reflectance infrared Fourier transform spectroscopy on CO adsorption (CO-DRIFTS) of Au NC/ZIF-8 revealed a higher valence state and a lower electron density of Au than that of Au NP/ZIF-8, combined with the desorption of azoxybenzene from the Au NC and Au NP surface, suggesting that the Au NCs with lower electron density exhibit stronger adsorption. Density functional theory (DFT) calculations and charge density difference maps indicated that azoxybenzene bonded to Au NC/ZIF-8 with greater adsorption energy, resulting in more electron transfer between azoxybenzene and the generated Au sites, which inhibited further reduction of azoxybenzene and resulted in high azoxybenzene selectivity. The application of the size effect of Au particles to regulate nitrobenzene transfer coupling provided new insights into the structure-selectivity relationships.
通过微调催化剂结构，实现了经由硝基芳烃化合物的转移偶联选择性合成有价值的偶氮和氧化偶氮芳烃化学品。在此，报道了一种通过利用金的尺寸效应来调节硝基苯还原并选择性地将产物从偶氮苯转变为氧化偶氮苯的直接方法。嵌入在ZIF-8中的较小尺寸的金纳米团簇（NCs）可控制地将硝基苯转化为氧化偶氮苯，而负载型金纳米颗粒（NPs）则选择性地催化硝基苯还原为偶氮苯。对Au NC/ZIF-8进行的X射线光电子能谱（XPS）和一氧化碳吸附漫反射红外傅里叶变换光谱（CO-DRIFTS）显示，与Au NP/ZIF-8相比，Au的价态更高且电子密度更低，同时氧化偶氮苯从Au NC和Au NP表面脱附，这表明电子密度较低的Au NCs表现出更强的吸附作用。密度泛函理论（DFT）计算和电荷密度差图表明，氧化偶氮苯与Au NC/ZIF-8结合时具有更大的吸附能，导致氧化偶氮苯与生成的Au位点之间有更多的电子转移，这抑制了氧化偶氮苯的进一步还原并导致了高氧化偶氮苯选择性。利用金颗粒的尺寸效应来调控硝基苯转移偶联为结构-选择性关系提供了新的见解。
