Chemistry Department, Faculty of Science, Assiut University, Assiut, 71515, Egypt.
Sci Rep. 2023 Jun 22;13(1):10123. doi: 10.1038/s41598-023-36627-x.
The missing-linker defects of UiO-66 were exploited to covalently anchor Cu nanoclusters (Cu/UiO-66). The molecular interactions between the metals and oxides as copper-zirconia interfaces in Cu/UiO-66 are essential for heterogeneous catalysis, leading to remarkable synergistic impacts on activity and selectivity. Homogeneously distributed carbonaceous mixed metal oxides (CuO/ZrO@C) nanocomposite was prepared via carbonization of the Cu/UiO-66 at 600 °C for 3 h in air. To enhance the acidity properties of the CuO/ZrO@C nanocomposite, a small amount of sulfuric acid was added and heated at 150 °C under an N atmosphere (CuO/ZrO-SOH@C). The synthesised Cu/UiO-66 and CuO/ZrO-SOH@C catalysts were used as novel catalysts in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The Cu/UiO-66 and CuO/ZrO-SOH@C catalysts displayed complete conversion of the 4-NP solution during (4 and 2 min) stirring at room temperature, respectively. These two catalysts exhibited a high reduction rate of 8.61 × 10 s, and 18.3 × 10 s, respectively. The X-ray photoelectron spectroscopic (XPS) analysis showed the charge of copper atoms in the Cu/UiO-66 catalyst was Cu/Cu and in the CuO/ZrO-SOH@C catalyst was Cu/Cu with nearly the same ratio (65/35). The particle size and the elemental composition of the CuO/ZrO-SOH@C catalyst were analysed by using high resolution transmission electron microscopy (HR-TEM), and energy-dispersive X-ray spectroscopy (EDS), and elemental mapping, respectively. The key point beyond the high catalytic activity and selectivity of the CuO/ZrO-SOH@C catalyst is both the carbon-metal oxides heterojunction structure that leads to good dispersion of the CuO and ZrO over the carbon sheets, and the high acidity properties that come from the combination between the Brønsted acid sites from sulfuric acid and Lewis acid sites from the UiO-66. The catalysts exhibited good recyclability efficiency without significant loss in activity, indicating their good potential for industrial applications.
采用 UiO-66 的缺链接缺陷将铜纳米簇（Cu/UiO-66）共价锚定。金属与氧化物之间的分子相互作用作为铜-氧化锆界面在 Cu/UiO-66 中对多相催化至关重要，导致活性和选择性的显著协同影响。通过在空气中将 Cu/UiO-66 在 600°C 下碳化 3 小时，制备了均匀分布的碳质混合金属氧化物（CuO/ZrO@C）纳米复合材料。为了增强 CuO/ZrO@C 纳米复合材料的酸性，加入少量硫酸并在 N 气氛下于 150°C 加热（CuO/ZrO-SOH@C）。合成的 Cu/UiO-66 和 CuO/ZrO-SOH@C 催化剂被用作新型催化剂，用于还原 4-硝基苯酚（4-NP）为 4-氨基酚（4-AP）。Cu/UiO-66 和 CuO/ZrO-SOH@C 催化剂在室温下搅拌（4 和 2 分钟）时，4-NP 溶液完全转化。这两种催化剂的还原速率分别为 8.61×10^-2 s 和 18.3×10^-2 s。X 射线光电子能谱（XPS）分析表明，Cu/UiO-66 催化剂中铜原子的电荷为 Cu/Cu，而 CuO/ZrO-SOH@C 催化剂中的电荷为 Cu/Cu，比例相近（65/35）。使用高分辨率透射电子显微镜（HR-TEM）、能量色散 X 射线光谱（EDS）和元素映射分别分析了 CuO/ZrO-SOH@C 催化剂的粒径和元素组成。CuO/ZrO-SOH@C 催化剂具有高催化活性和选择性的关键在于碳-金属氧化物异质结结构，该结构导致 CuO 和 ZrO 在碳片上的良好分散，以及高酸性，这来自于硫酸的 Brønsted 酸位和 UiO-66 的路易斯酸位的结合。催化剂表现出良好的可回收效率，活性无明显损失，表明其在工业应用方面具有良好的潜力。
